A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance...

343
A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences University of Technology, Sydney Lit: Platen, E. & Heath, D.: A Benchmark Approach to Quantitative Finance Springer Finance, 700 pp., 199 illus., Hardcover, ISBN-10 3-540-26212-1 (2006). Platen, E.: A benchmark approach to finance. Mathematical Finance 16(1), 131-151 (2006). uhlmann, H. & Platen, E.: A discrete time benchmark approach for insurance and finance ASTIN Bulletin 33(2), 153-172 (2003).

Transcript of A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance...

Page 1: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

A Benchmark Approach to Quantitative Finance

Eckhard PlatenSchool of Finance and Economics and Department of Mathematical Sciences

University of Technology, Sydney

Lit: Platen, E. & Heath, D.: A Benchmark Approach to Quantitative Finance

Springer Finance, 700 pp., 199 illus., Hardcover, ISBN-10 3-540-26212-1 (2006).

Platen, E.: A benchmark approach to finance. Mathematical Finance16(1), 131-151 (2006).

Buhlmann, H. & Platen, E.: A discrete time benchmark approach for insurance and finance

ASTIN Bulletin33(2), 153-172 (2003).

Page 2: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

Contents1 Asset Pricing 1

2 Continuous Financial Markets 55

3 Portfolio Optimization 91

4 Modeling Stochastic Volatility 107

5 Minimal Market Model 154

6 Stylized Multi-Currency MMM 214

7 Valuing Guaranteed Minimum Death Benefits 219

8 Markets with Event Risk 273

References 337

Page 3: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

1 Asset Pricing

Law of One Price

“All replicating portfolios of a payoff have the same price!”

Debreu (1959), Sharpe (1964), Lintner (1965),

Merton (1973a, 1973b), Ross (1976), Harrison & Kreps (1979),

Cochrane (2001),. . .

will be, in general, violated under the benchmark approach.

c© Copyright Eckhard Platen 10 BA - Toronto C 1 1

Page 4: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

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1

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time

ln(savings bond)ln(fair zero coupon bond)

ln(savings account)

Figure 1.1: Logarithms of savings bond, fair zero coupon bondand savings

account.c© Copyright Eckhard Platen 10 BA - Toronto C 1 2

Page 5: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

Financial Market

• jth primary security account

Sjt

j ∈ 0, 1, . . . , d

• savings account

S0t

t ≥ 0

c© Copyright Eckhard Platen 10 BA - Toronto C 1 3

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• strategy

δ = δt = (δ0t , δ1t , . . . , δ

dt )⊤, t ≥ 0

predictable

• portfolio

Sδt =

d∑

j=0

δjt S

jt

• self-financing

dSδt =

d∑

j=0

δjt dS

jt

c© Copyright Eckhard Platen 10 BA - Toronto C 1 4

Page 7: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• strictly positive portfolio

Sδ0 = x > 0

Sδt ∈ (0,∞) for all t ∈ [0,∞)

=⇒ Sδ ∈ V+x

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Page 8: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

Numeraire Portfolio

Definition 1.1 Sδ∗ ∈ V+x numeraire portfolioif

Et

Sδt+h

Sδ∗

t+h

Sδt

Sδ∗

t

− 1

≤ 0

for all nonnegativeSδ and t, h ∈ [0,∞).

• Sδ∗ “best” performing portfolio

Long (1990), Becherer (2001), Pl. (2002, 2006),

Buhlmann& Pl. (2003), Goll & Kallsen (2003), Karatzas & Kardaras (2007)

c© Copyright Eckhard Platen 10 BA - Toronto C 1 6

Page 9: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

Main Assumption of the Benchmark Approach

Assumption 1.2 There exists a numeraire portfolioSδ∗ ∈ V+x .

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Page 10: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

EWI

MCI

DWI

WSI

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

1/1/73 28/9/76 25/6/80 22/3/84 18/12/87 15/9/91 12/6/95 9/3/99 4/12/02 31/8/06

$US

Figure 1.2: Constructed MCI, DWI, EWI and WSI. In the long term the WSI

and EWI outperform all other indices, Le& Platen (2006).

c© Copyright Eckhard Platen 10 BA - Toronto C 1 8

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• benchmarked value

Sδt =

Sδt

Sδ∗

t

Supermartingale Property

Corollary 1.3 For nonnegativeSδ

Sδt ≥ Et

(

Sδs

)

0 ≤ t ≤ s < ∞

Sδ supermartingale

c© Copyright Eckhard Platen 10 BA - Toronto C 1 9

Page 12: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• long term growth rate

gδ = lim supt→∞

1

tln

(

Sδt

Sδ0

)

Theorem 1.4 For Sδ ∈ V+x

gδ ≤ gδ∗ .

• “pathwise best” in the long run

Karatzas & Shreve (1998), Pl. (2004a),

Karatzas & Kardaras (2007)

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Page 13: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

Pl. (2004a)

Definition 1.5 Nonnegative portfolioSδ outperforms systematicallySδ if

(i) Sδ0 = Sδ

0 ;

(ii) P(

Sδt ≥ Sδ

t

)

= 1

(iii) P(

Sδt > Sδ

t

)

> 0.

• “relative arbitrage” Fernholz & Karatzas (2005)

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Page 14: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

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-1

0

1

1930 1940 1950 1960 1970 1980 1990 2000

time

ln(fair zero coupon bond)ln(savings account)

Figure 1.3: Logarithms of fair zero coupon bond and savings account.

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Page 15: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

Theorem 1.6 Numeraire portfolio cannot be outperformed systematically.

c© Copyright Eckhard Platen 10 BA - Toronto C 1 13

Page 16: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• portfolio ratio

Aδt,h =

Sδt+h

Sδt

• expected growth

gδt,h = Et

(

ln(

Aδt,h

))

t, h ≥ 0

c© Copyright Eckhard Platen 10 BA - Toronto C 1 14

Page 17: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

Definition 1.7 Sδ growth optimal if

gδt,h ≤ g

δt,h

for all t, h ≥ 0 and nonnegativeSδ.

• expected log-utility

Kelly (1956)

Hakansson (1971a)

Merton (1973a)

Roll (1973)

Markowitz (1976)

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Page 18: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

Theorem 1.8 The numeraire portfolio is growth optimal.

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Page 19: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

Strong Arbitrage

• market participants can only exploit arbitrage

• limited liability

=⇒ nonnegative total wealth of each market participant

Definition 1.9 A nonnegativeSδ is a strong arbitrageif Sδ0 = 0 and

P(

Sδt > 0

)

> 0.

Pl. (2002)-mathematical arguments (super-martingale property)

Loewenstein & Willard (2000)-economic arguments

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Page 20: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

Theorem 1.10 There isno strong arbitrage.

c© Copyright Eckhard Platen 10 BA - Toronto C 1 18

Page 21: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• Delbaen & Schachermayer (1998)

free lunches with vanishing risk (FLVR)

• Loewenstein & Willard (2000)

free snacks& cheap thrills

=⇒ no-arbitrage pricing makes no sense under BA

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Page 22: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

-0.2

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1

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time

Figure 1.4:P (t, T ) minus savings account.

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Page 23: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

-0.0004

-0.0002

0

0.0002

0.0004

0.0006

0.0008

0.001

0.0012

0.0014

0.0016

0.0018

1920 1922 1924 1926 1928

time

Figure 1.5:P (t, T ) minus savings account.

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Page 24: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• Existence of equivalent risk neutral probability measure is

more amathematical conveniencethan an economic necessity.

• Basing quantitative methods on classical risk neutral pricing is

restrictive.

• Trends are ignored under

Fundamental Theorem of Asset Pricing

Delbaen & Schachermayer (1998)

c© Copyright Eckhard Platen 10 BA - Toronto C 1 22

Page 25: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• Equivalent to risk neutral pricing are pricing via:

stochastic discount factor, Cochrane (2001);

deflator, Duffie (2001);

pricing kernel , Constantinides (1992);

state price density, Ingersoll (1987);

numeraire portfolio as in Long (1990)

All ignore trends !

c© Copyright Eckhard Platen 10 BA - Toronto C 1 23

Page 26: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• One needs consistent pricing concept that exploits trends

• All benchmarked nonnegative securities are supermartingales

(no upward trend)

c© Copyright Eckhard Platen 10 BA - Toronto C 1 24

Page 27: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

Definition 1.11 Price is fair if, when benchmarked, forms martingale

(no trend)

Sδt = Et

(

Sδs

)

0 ≤ t ≤ s < ∞.

c© Copyright Eckhard Platen 10 BA - Toronto C 1 25

Page 28: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

Lemma 1.12 Theminimal nonnegative supermartingale that reaches a

given benchmarked contingent claimis a martingale.

see Pl.& Heath (2006)

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Page 29: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

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time

benchmarked savings bondbenchmarked fair zero coupon bond

Figure 1.6: Benchmarked savings bond and benchmarked fair zero coupon

bond.c© Copyright Eckhard Platen 10 BA - Toronto C 1 27

Page 30: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

Law of the Minimal Price

Pl. (2008)

Theorem 1.13 If a fair portfolio replicates a nonnegative payoff, then this

represents the minimal replicating portfolio.

• least expensive

• minimal hedge

• economically correct price in a competitive market

c© Copyright Eckhard Platen 10 BA - Toronto C 1 28

Page 31: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• contingent claim

HT

E0

(

HT

Sδ∗

T

)

< ∞

• SδH

t fair if

SδH

t =SδH

t

Sδ∗

t

= Et

(

HT

Sδ∗

T

)

Link with real economy !

c© Copyright Eckhard Platen 10 BA - Toronto C 1 29

Page 32: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

Law of the Minimal Price =⇒

Corollary 1.14

Minimal price for replicableHT is fair and given by

real world pricing formula

SδH

t = Sδ∗

t Et

(

HT

Sδ∗

T

)

.

c© Copyright Eckhard Platen 10 BA - Toronto C 1 30

Page 33: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• most pricing concepts are unified and generalized by real world pricing

=⇒

actuarial pricing

risk neutral pricing

pricing with stochastic discount factor

pricing with numeraire change

pricing with deflator

pricing with state pricing density

pricing with pricing kernel

pricing with numeraire portfolio

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Page 34: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

WhenHT independentof Sδ∗

T

=⇒ rigorous derivation of

• actuarial pricing formula

SδH

t = P (t, T )Et(HT )

with zero coupon bond

P (t, T ) = Sδ∗

t Et

(

1

Sδ∗

T

)

c© Copyright Eckhard Platen 10 BA - Toronto C 1 32

Page 35: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• real world pricing formula =⇒

SδH

0 = E0

(

ΛT

S00

S0T

HT

)

Λt =S0

t

S00

supermartingale

1 = Λ0 ≥ E0(ΛT )

=⇒

SδH

0 ≤E0

(

ΛTS0

0

S0T

HT

)

E0(ΛT )

similar for any numeraire (hereS0 savings account)

c© Copyright Eckhard Platen 10 BA - Toronto C 1 33

Page 36: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

0

10

20

30

40

50

60

70

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90

100

1930 1940 1950 1960 1970 1980 1990 2000

time

Figure 1.7: Discounted S&P500 total return index.

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Page 37: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

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1.8

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time

Radon-Nikodym derivativeTotal RN-Mass

Figure 1.8: Radon-Nikodym derivative and total mass of putative risk neutral

measure.c© Copyright Eckhard Platen 10 BA - Toronto C 1 35

Page 38: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• special case whensavings account is fair:

=⇒ ΛT = dQ

dPforms martingale; E0(ΛT ) = 1;

equivalent risk neutral probability measureQ exists;

Bayes’ formula =⇒risk neutral pricing formula

SδH

0 = EQ0

(

S00

S0T

HT

)

Harrison & Kreps (1979), Ingersoll (1987),

Constantinides (1992), Duffie (2001), Cochrane (2001),. . .

• otherwise “risk neutral price”≥ real world price

c© Copyright Eckhard Platen 10 BA - Toronto C 1 36

Page 39: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

-1

0

1

2

3

4

5

6

7

8

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1930 1940 1950 1960 1970 1980 1990 2000

time

ln(index)ln(savings account)

Figure 1.9: ln(S&P500 accumulation index) and ln(savings account).

c© Copyright Eckhard Platen 10 BA - Toronto C 1 37

Page 40: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

Extreme Maturity Bond

• short rate deterministic

• savings bond

P ∗(t, T ) =S0

t

S0T

• index S1 as numeraire portfolioSδ∗

c© Copyright Eckhard Platen 10 BA - Toronto C 1 38

Page 41: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• fair zero coupon bond

Law of the Minimal Price

=⇒ real world pricing formula

P (t, T ) = Sδ∗

t Et

(

1

Sδ∗

T

)

• benchmarked fair zero coupon bond

P (t, T ) =P (t, T )

Sδ∗

t

martingale

c© Copyright Eckhard Platen 10 BA - Toronto C 1 39

Page 42: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• discounted numeraire portfolio

Sδ∗

t =Sδ∗

t

S0t

numeraire portfolio for continuous market:

dSδ∗

t = αt dt+

Sδ∗

t αt dWt

time transformed squared Bessel process

c© Copyright Eckhard Platen 10 BA - Toronto C 1 40

Page 43: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• model the drift of discounted index as

αt = α expη t=⇒

Sδ∗

t time transformed squared Bessel process of dimension four

=⇒ Minimal Market Model

MMM, see Pl.& Heath (2006)

• net growth rate

η ≈ 0.054 with R2 of 0.89

c© Copyright Eckhard Platen 10 BA - Toronto C 1 41

Page 44: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

-2

-1

0

1

2

3

4

5

1930 1940 1950 1960 1970 1980 1990 2000

time

ln(discounted index)trendline

Figure 1.10: Logarithm of discounted S&P500 and trendline.

c© Copyright Eckhard Platen 10 BA - Toronto C 1 42

Page 45: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• normalized index

Yt =Sδ∗

t

αt

dYt = (1 − η Yt) dt+√

Yt dWt

• quadratic variation of√Yt

d√

Yt = . . .+1

2dWt

it∑

ℓ=1

(

Ytℓ−√

Ytℓ−1

)2

≈[√Y]

t=t

4

• scaling parameter α ≈ 0.01468 with R2 of 0.995

c© Copyright Eckhard Platen 10 BA - Toronto C 1 43

Page 46: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

0

5

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15

20

25

30

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time

[sqrt Y]trendline

Figure 1.11: Quadratic Variation of√Yt.

c© Copyright Eckhard Platen 10 BA - Toronto C 1 44

Page 47: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• fair zero coupon bond

P (t, T ) = P ∗(t, T )

(

1 − exp

− 2 η Sδ∗

t

α (expη T − expη t)

)

• initial prices

P ∗(0, T ) = 0.0335

P (0, T ) = 0.00077

P (0,T )P ∗(0,T )

< 0.023 =⇒ 2.3%

no strong arbitrage

c© Copyright Eckhard Platen 10 BA - Toronto C 1 45

Page 48: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

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time

benchmarked savings bondbenchmarked fair zero coupon bond

Figure 1.12: Benchmarked savings bond and benchmarked fair zero coupon

bond.c© Copyright Eckhard Platen 10 BA - Toronto C 1 46

Page 49: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

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1

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time

savings bondfair zero coupon bond

savings account

Figure 1.13: Savings bond, fair zero coupon bond and savings account.

c© Copyright Eckhard Platen 10 BA - Toronto C 1 47

Page 50: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

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0

1

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time

ln(savings bond)ln(fair zero coupon bond)

Figure 1.14: Logarithms of fair zero coupon bond and savings account.

c© Copyright Eckhard Platen 10 BA - Toronto C 1 48

Page 51: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• savings account isoutperformed systematically

by fair zero coupon bond

c© Copyright Eckhard Platen 10 BA - Toronto C 1 49

Page 52: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

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-1

0

1

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time

ln(fair zero coupon bond)ln(savings account)

Figure 1.15: Logarithms of fair zero coupon bond and savings account.

c© Copyright Eckhard Platen 10 BA - Toronto C 1 50

Page 53: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• self-financing hedge portfoliohedge ratio

δ∗t =

∂P (t, T )

∂Sδ∗

t

= P ∗(0, T ) exp

−2 η Sδ∗

t

α (expη T − expη t)

× 2 η

α (expη T − expη t)

c© Copyright Eckhard Platen 10 BA - Toronto C 1 51

Page 54: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

-8

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-6

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-1

0

1

1930 1940 1950 1960 1970 1980 1990 2000

time

ln(zero coupon bond)ln(self financing hedge portfolio)

Figure 1.16: Logarithm of zero coupon bond and self-financinghedge port-

folio.c© Copyright Eckhard Platen 10 BA - Toronto C 1 52

Page 55: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

-2e-005

-1e-005

0

1e-005

2e-005

3e-005

4e-005

5e-005

6e-005

7e-005

1930 1940 1950 1960 1970 1980 1990 2000

time

Figure 1.17: Benchmarked profit and loss.

c© Copyright Eckhard Platen 10 BA - Toronto C 1 53

Page 56: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

0

0.2

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0.6

0.8

1

1930 1940 1950 1960 1970 1980 1990 2000

time

Figure 1.18: Fraction invested in the index.

c© Copyright Eckhard Platen 10 BA - Toronto C 1 54

Page 57: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

2 Continuous Financial Markets

• d sources of continuoustraded uncertainty

independent standard Wiener processes

W 1,W 2, . . . ,W d, d ∈ 1, 2, . . .

c© Copyright Eckhard Platen 10 BA - Toronto C 2 55

Page 58: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

Primary Security Accounts

Sjt - jth primary security account at timet,

j ∈ 0, 1, . . . , d

cum-dividend share value or savings account value,

dividends or interest are accumulated, reinvested

• vector process of primary security accounts

S = St = (S0t , . . . , S

dt )⊤, t ∈ [0, T ]

c© Copyright Eckhard Platen 10 BA - Toronto C 2 56

Page 59: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• assumeunique strong solutionof SDE

dSjt = Sj

t

(

ajt dt+

d∑

k=1

bj,kt dW k

t

)

t ∈ [0,∞), Sj0 > 0, j ∈ 1, 2, . . . , d

• predictable, integrable appreciation rate processesaj

• predictable, square integrable volatility processesbj,k

c© Copyright Eckhard Platen 10 BA - Toronto C 2 57

Page 60: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• savings account

S0t = exp

∫ t

0

rs ds

predictable, integrable short rate process

r = rt, t ∈ [0,∞)

c© Copyright Eckhard Platen 10 BA - Toronto C 2 58

Page 61: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• Market price of risk

The unique invariant of the market

θt = (θ1t , θ

2t , . . . , θ

dt )⊤

solution of relation

bt θt = at − rt 1

where

at = (a1t , a

2t , . . . , a

dt )

1 = (1, 1, . . . , 1)⊤

c© Copyright Eckhard Platen 10 BA - Toronto C 2 59

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Assumption 2.1

Volatility matrixbt = [bj,kt ]dj,k=1 is invertible

=⇒• market price of risk equals

θt = b−1t (at − rt 1)

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• rewritejth primary security account SDE

dSjt = Sj

t

rt dt+d∑

k=1

bj,kt (θk

t dt+ dW kt )

t ∈ [0,∞), j ∈ 1, 2, . . . , d

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• strategy

δ = δt = (δ0t , . . . , δdt )⊤, t ∈ [0, T ]

predictable andS-integrable,

δjt number of units ofjth primary security account

• portfolio

Sδt =

d∑

j=0

δjt S

jt

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• Sδ self-financing⇐⇒

dSδt =

d∑

j=0

δjt dS

jt

changes in the portfolio value only due to gains from trading,

self-financing in each denomination

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• jth fraction

πjδ,t = δj

t

Sjt

Sδt

j ∈ 0, 1, . . . , d

d∑

j=0

πjδ,t = 1

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• portfolio SDE

dSδt = Sδ

t

(

rt dt+

d∑

k=1

bkδ,t

(

θkt dt+ dW k

t

)

)

with kth portfolio volatility

bkδ,t =

d∑

j=1

πjδ,t b

j,kt

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• logarithm of strictly positive portfolio

d ln(Sδt ) = gδ

t dt+

d∑

k=1

bkδ,t dW

kt

with growth rate

gδt = rt +

d∑

k=1

bkδ,t

(

θkt − 1

2bk

δ,t

)

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Numeraire Portfolio Sδ∗ = Growth Optimal Portfolio

=⇒ maximize the growth rate

gδt = rt +

d∑

k=1

d∑

j=1

πjδ,t b

j,kt

(

θkt − 1

2

d∑

ℓ=1

πℓδ,t b

ℓ,kt

)

=⇒ for eachj ∈ 1, 2, . . . , d

0 =

d∑

k=1

bj,kt

(

θkt −

d∑

ℓ=1

πℓδ∗,t b

ℓ,kt

)

=⇒θ⊤

t = π⊤δ∗,t bt

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Sincebt invertible=⇒

πδ∗,t = (π1δ∗,t, . . . , π

dδ∗,t)

= (b−1t )⊤ θt

=⇒ NP

dSδ∗

t = Sδ∗

t

([

rt +

d∑

k=1

(θkt )2

]

dt+

d∑

k=1

θkt dW

kt

)

finite NP exists

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Benchmarked Portfolios

Sδt =

Sδt

Sδ∗

t

dSδt = Sδ

t

rt dt+

d∑

k=1

d∑

j=0

πjδ,t b

j,kt

(

θkt dt+ dW k

t

)

dSδ∗

t = Sδ∗

t

(

rt dt+d∑

k=1

θkt

(

θkt dt+ dW k

t

)

)

dSδt = −Sδ

t

d∑

k=1

d∑

j=0

πjδ,t s

j,kt dW k

t

driftless =⇒ local martingale =⇒ supermartingalewhen nonnegative

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Theorem 2.2 Any nonnegative benchmarked portfolio is an

(A, P )-supermartingale(no upward trend).

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=⇒ NP is numeraire portfolio

use NP asbenchmark for investment and asnumeraire for pricing

• markets have thousands of primary security accounts

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Example of a Multi-Asset BS Model

• jth primary security account

dSjt = Sj

t

[

(

r + σ2

(

1 +1√d

))

dt+σ√d

d∑

k=1

dW kt + σ dW j

t

]

t ∈ [0, T ], j ∈ 1, 2, . . . , d, σ > 0

general market risk, specific market risk

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• NP fractions

πjδ∗,t =

(√d(

1 +√d))−1

j ∈ 1, 2, . . . , d

π0δ∗,t =

(

1 +√d)−1

• NP SDE

dSδ∗

t = Sδ∗

t

(

(

r + σ2)

dt+σ√d

d∑

k=1

dW kt

)

• simulate overT = 32 yearsd = 50 risky primary security accounts

σ = 0.15, r = 0.05

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0

5

10

15

20

25

0 5 10 15 20 25 30 35

time

Figure 2.1: Simulated primary security accounts.

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0

1

2

3

4

5

6

7

8

9

10

0 5 10 15 20 25 30 35

time

GOPB

Figure 2.2: Simulated NP and savings account.

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Diversified Portfolios

Fundamental phenomenon ofdiversification leads naturally toNP:

diversified =⇒ fractions “small”

Definition 2.3 A strictly positive portfolioSδ is adiversified portfolio if

∣πj

δ,t

∣≤ K2

d12+K1

a.s. for allj ∈ 0, 1, . . . , d andt ∈ [0, T ] for K1,K2 ∈ (0,∞) and

K3 ∈ 1, 2, . . ., independent ofd ∈ K3,K3 + 1, . . ..

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• jth benchmarked primary security account

Sjt =

Sjt

Sδ∗

t

dSjt = −Sj

t

d∑

k=1

sj,kt dW k

t

• (j, k)th specific volatility

sj,kt = θk

t − bj,kt

measuresspecific market risk of Sj with respect toW k

• θkt measuresgeneral market risk with respect toW k

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• kth total specific absolute volatility

skt =

d∑

j=0

|sj,kt |

regular =⇒ variance of specific returns “bounded”

Definition 2.4 A market is calledregular if

E(

(

skt

)2)

≤ K5.

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Tracking Rate

Variance of benchmarked portfolio returns

Rdδ(t) =

d∑

k=1

d∑

j=0

πjδ,t s

j,kt

2

Rdδ(t) - quantifies distance betweenSδ and Sδ∗

benchmarked NP constant=⇒

Rdδ∗

(t) = 0

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Approximate NP

tracking rate “small”

Definition 2.5 A strictly positive portfolioSδ is an approximate NP if

for all t ∈ [0, T ] and ε > 0

limd→∞

P(

Rdδ(t) > ε

)

= 0.

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Diversification Theorem

Theorem 2.6 In a regular market

any diversified portfolio is an approximate NP.

• model independent

• similarity to CLT

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Equal Weighted Index (EWI)

SδEWI holds equal fractions

πjδEWI,t

=1

d+ 1

j ∈ 0, 1, . . . , d

• tracking rate for multi-asset BS example:

RdδEWI

(t) =

d∑

k=1

(

1

d+ 1

(

θkt − bk,k

t

)

)2

= d

(

1

d+ 1

(

σ√d

− σ

))2

≤ σ2

(d+ 1)→ 0

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0

1

2

3

4

5

6

7

8

9

10

0 5 10 15 20 25 30 35

time

GOPEWI

Figure 2.3: Simulated NP and EWI.

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0

1

2

3

4

5

6

7

8

9

10

0 5 10 15 20 25 30 35

time

GOPindex

Figure 2.4: Simulated diversified accumulation index and NP.

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0

20,000

40,000

60,000

80,000

100,000

120,000

1/1/73 28/9/76 25/6/80 22/3/84 18/12/87 15/9/91 12/6/95 9/3/99 4/12/02 31/8/06

Figure 2.5: World industry sector stock market indices as primary security

accounts.

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EWI

MCI

DWI

WSI

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

1/1/73 28/9/76 25/6/80 22/3/84 18/12/87 15/9/91 12/6/95 9/3/99 4/12/02 31/8/06

$US

Figure 2.6: Constructed MCI, DWI, EWI and WSI. In the long term the WSI

and EWI outperform all other indices, Le& Platen (2006).

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0

50

100

150

200

250

300

350

400

450

0 5 9 14 18 23 27 32

Figure 2.7: Primary security accounts under the MMM.

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0

10

20

30

40

50

60

0 5 9 14 18 23 27 32

Figure 2.8: Benchmarked primary security accounts.

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0

10

20

30

40

50

60

70

80

90

100

0 5 9 14 18 23 27 32

EWI

GOP

Figure 2.9: NP and EWI.

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0

10

20

30

40

50

60

70

80

90

100

0 5 9 14 18 23 27 32

Market index

GOP

Figure 2.10: NP and market index.

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3 Portfolio Optimization

• NP best long term investment

Kelly (1956), Latane (1959), Breiman (1961),

Hakansson (1971b), Thorp (1972)

• optimal portfolio separated into two funds

Tobin (1958), Sharpe (1964)

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• mean-variance efficient portfolio

Markowitz (1959)

• intertemporal capital asset pricing model

Merton (1973a)

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Expected Utility Maximization

• utility function U(·), U ′(·) > 0 U ′′(·) < 0

• examples

power utility

U(x) =1

γxγ

for γ 6= 0 andγ < 1

log-utility

U(x) = ln(x)

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5 10 15 20x

-15

-10

-5

5

U

Figure 3.1: Examples for power utility (upper graph) and log-utility (lower

graph).

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• assumeS0 is scalar diffusion

• maximize expected utility

vδ = maxSδ∈V+

S0

E0

(

U(

SδT

))

V+S0

strictly positive, discounted, fair portfolios

Sδ0 = S0 > 0

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Theorem 3.1

Benchmarked, expected utility maximizing portfolio:

Sδt = u(t, S0

t ) = Et

(

U ′−1(

λ S0T

)

S0T

)

,

λ s.t. S0 = Sδ0 S

δ∗

0 = u(0, S0)Sδ∗

0

two fund separation with risk aversion coefficient

J δt =

1

1 − S0t

u(t,S0t )

∂u(t,S0t )

∂S0t

=⇒ invest 1

J δt

of wealth in NP and remainder in savings account

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• log-utility function U(x) = ln(x)

U ′(x) =1

x

U ′−1(y) =1

y

U ′′(x) = − 1

x2

utility concave

u(t, S0t ) = Et

(

U ′−1(

λ S0T

)

S0T

)

= Et

(

1

λ S0T

S0T

)

=1

λ

Lagrange multiplier

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λ =Sδ∗

0

S0

risk aversion coefficient

J δt = 1

• expected log-utility

vδ = E0

(

ln(

Sδ∗

T

))

= ln(λ) + ln(S0) +1

2

∫ T

0

E0

(

(

θ(s, Sδ∗

s ))2)

ds

if local martingale part forms a martingale

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• power utility

U(x) =1

γxγ

for γ < 1, γ 6= 0

U ′(x) = xγ−1

U ′−1(y) = y1

γ−1

U ′′(x) = (γ − 1)xγ−2

concave

u(t, S0t ) = Et

(

λ

Sδ∗

T

)1

γ−11

Sδ∗

T

= λ1

γ−1 Et

(

(

Sδ∗

T

1−γ

)

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Sδ∗ geometric Brownian motion

u(t, S0t ) = λ

1γ−1

(

Sδ∗

t

)

γ1−γ

×Et

(

exp

γ

1 − γ

(

θ2

2(T − t) + θ (WT −Wt)

))

= λ1

γ−1(

Sδ∗

t

)

γ1−γ exp

θ2

2

γ

(1 − γ)2(T − t)

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Lagrange multiplier

λ = Sγ−10 Sδ∗

0 exp

θ2

2

γ

1 − γT

S0t = (Sδ∗

t )−1

∂u(t, S0t )

∂S0=u(t, S0

t )

S0t

γ

γ − 1

=⇒ risk aversion coefficient

J δt = 1 − γ

expected utility

vδ = E0

(

1

γ

(

SδT

)γ)

= exp

−θ2

2

γ

1 − γT

(S0)γ

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Utility Indifference Pricing

discounted payoff H = HS0

T

(not perfectly hedgable)

vδε,V = E0

(

U

(

(S0 − ε V )Sδ

T

S0

+ ε H

))

• assumeS0 is scalar diffusion

Definition 3.2 utility indifference price V s.t.

limε→0

vδε,V − vδ

0,V

ε= 0

Davis (1997)

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• Taylor expansion

vδε,V ≈ E0

(

U(

SδT

)

+ εU ′(

SδT

)

(

H − V SδT

S0

))

= vδ0,V + εE0

(

U ′(

SδT

)

H)

− V εE0

(

U ′(

SδT

) SδT

S0

)

SδT = Sδ

T /S0T = U ′−1

(

λ S0T

)

=⇒

vδε,V − vδ

0,V = ε

(

E0

(

λ S0T H

)

− V E0

(

λ S0T

SδT

S0

))

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=⇒• utility indifference price

V =E0

(

λ

Sδ∗

T

H)

E0

(

λ

Sδ∗

T

SδT

S0

) =E0

(

H

Sδ∗

T

)

1S0

S0

Sδ∗

0

independent ofU and of given model =⇒

• real world pricing formula

V = Sδ∗

0 E0

(

H

Sδ∗

T

)

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Hedging

• benchmarked derivative price

UH(t) = Et

(

H

Sδ∗

T

)

• real world martingale representation

H

Sδ∗

T

= UH(t) +

d∑

k=1

∫ T

t

xkH(s) dW k

s +MH(t)

MH -orthogonal martingale

E([

MH ,Wk]

t

)

= 0

Follmer-Schweizer decomposition, Follmer & Schweizer (1991)

least square projection

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Theorem 3.3 Derivative price

SδH

t = Sδ∗

t Et

(

H

Sδ∗

T

)

fractions

πδH(t) =

(

bδH(t)⊤ b−1

t

)⊤

with portfolio volatilities

bkδH

(t) =1

UH(t)

d∑

j=0

δjH(t) Sj

t bj,kt =

xkH(t)

UH(t)+ θk

t .

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4 Modeling Stochastic Volatility

• consider well diversified accumulation index≈ NP

dSδ∗

t = Sδ∗

t

(

rt dt+ |θt|(

|θt| dt+ dWt

))

d ln(

Sδ∗

t

)

=

(

rt dt+1

2|θt|2

)

dt+ |θt| dWt

• volatility

|θt| =

d

dt[ln (Sδ∗)]t

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0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

1982 1992 2002

time

Figure 4.1: Estimated volatility of WSI from 1973–2004.

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Log-Returns of a Stock Index

-10 -5 0 5 10

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Figure 4.2: Histogram for S&P500 hourly deseasonalized log-returns.

fitted Gaussian density, much fatter tails

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Implied Volatilities

• European call for Black-Scholes model

cτ,K(0, S, σ)

maturity τ ∈ [0, T ]

strike priceK > 0

underlying indexS > 0

volatility σ

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• observed European call option price

Vc,τ,K(0, S0)

• implied volatility

σcallBS (0, S0, τ,K)

obtained such that

Vc,τ,K(0, S0) = cτ,K

(

0, S0, σcallBS (0, S0, τ,K)

)

by some root finding method

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100

200

300

time 0.6

0.8

1

1.2

1.4

moneyness

20

40

60

100

200

300

time

Figure 4.3: Implied volatilities for S&P500 three month options.

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implied volatility surface

0.5

0.75

1

1.25

1.5

KS

0.20.4

0.60.8

11.2

1.41.6T

0.22

0.24

0.26

0.28

0.5

0.75

1

1.25KS

0.20.4

0.60.8

11.2

1.4

Figure 4.4: Average S&P500 implied volatility surface.

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A Modified Constant Elasticity of Variance Model

• CEV Model

Cox (1975), Cox & Ross (1976)

Andersen & Andreasen (2000)

Lewis (2000)

Lo, Yuen & Hui (2000)

Brigo & Mercurio (2005)

Heath& Pl. (2005b)

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• classical risk neutral CEV

Beckers (1980)

Schroder (1989)

Delbaen & Shirakawa (2002)

certain problems in risk neutral pricing of derivatives

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Modified CEV Model

Heath& Pl. (2005b)

• savings account

dS0t = r S0

t dt

total market price for risk process

θt ≥ 0, t ∈ [0, T ]

• drifted Wiener process

dWθ(t) = θt dt+ dWt

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• NP

dSδ∗

t = Sδ∗

t (rt dt+ θt dWθ(t))

• NP volatility

θt = (Sδ∗

t )a−1 ψ

exponenta ∈ (−∞,∞)

scaling parameterψ > 0

stochastic fora 6= 1

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• hypothetical risk neutral CEV dynamics

dSδ∗

t = Sδ∗

t rt dt+ (Sδ∗

t )a ψ dWθ(t)

Wθ - Wiener process under a hypothetical risk neutral measurePθ

• If a = 1 =⇒ BS model

=⇒ equivalent risk neutral probability measurePθ

with market price of riskθt = ψ

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• real world CEV dynamics

dSδ∗

t =(

Sδ∗

t rt +(

Sδ∗

t

)2a−1ψ2)

dt+(

Sδ∗

t

)aψ dWt

modified CEV model remains fora < 1 strictly positive

this isnot the case for its “risk neutral” dynamics

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• squared Bessel process

Xt =(

Sδ∗

t

)2 (1−a)

for a 6= 1 with SDE

dXt =(

2(1 − a) rtXt + ψ2 (1 − a) (3 − 2a))

dt

+2ψ (1 − a)√

Xt dWt

anddimension

δ =3 − 2 a

1 − a

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• Radon-Nikodym derivative process

Λθ = Λθ(t), t ∈ [0, T ](state price density)

• hypothetical risk neutral measurePθ

dPθ

dP= Λθ(T )

Λθ(t) =Sδ∗

0

Sδ∗

t

S0t =

(

X0

Xt

)q

S0t

q =1

2 (1 − a)

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• squared Bessel process

dXt =(

2 (1 − a) rtXt + ψ2 (1 − a)(1 − 2 a))

dt

+2ψ (1 − a)√

Xt dWθ(t)

dimension

δθ =1 − 2 a

1 − a

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• dimension

risk neutral

δθ =1 − 2 a

1 − a

real world

δ =3 − 2 a

1 − a

• if a < 1 =⇒ δ > 2 andδθ < 2

if a > 1 =⇒ δ < 2 andδθ > 2

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-1 0 1 2 3

-4

-2

0

2

4

6

8

Risk Neutral

Real World

Figure 4.5: Dimensionsδ andδθ as a function of the exponenta.

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• hypothetical risk neutral probability

Pθ(A) =

A

dPθ(ω) =

A

dPθ(ω)

dP (ω)dP (w)

=

A

Λθ(T ) dP (ω)

=⇒

Pθ(Ω) =

Ω

Λθ(T ) dP (ω) = E0 (Λθ(T ))

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• for a < 1 =⇒ δθ < 2

=⇒ Λθ is strict supermartingale =⇒

Pθ(Ω) < Λθ(0) = 1

=⇒ Pθ is not a probability measure

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• for a 6= 1 P andPθ are not equivalent

=⇒ modified CEV model doesnot haveequivalent risk neutral

probability measure

• consider onlya < 1 since fora > 1 NP explodes

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Real World Pricing

• contingent claim

Hτ = Hτ (Sδ∗

τ ), E

(

Sδ∗

τ

)

< ∞

• fair price

uHτ(t, Sδ∗

t ) = Sδ∗

t uHτ(t, Sδ∗

t )

benchmarked price

uHτ(t, Sδ∗

t ) = Et

(

Hτ (Sδ∗

τ )

Sδ∗

τ

)

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Martingale Representation

Sδ∗

τ

= uHτ(τ, Sδ∗

τ )

= uHτ(t, Sδ∗

t ) +

∫ τ

t

(

Sδ∗

s

)aψ∂uHτ

(s, Sδ∗

s )

∂Sδ∗

dWs

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Stochastic Volatility Models

• volatility function of underlying diffusion=⇒ LV model

• volatility as separate, possibly correlated process

Hull & White (1987, 1988)Johnson & Shanno (1987)Scott (1987)Wiggins (1987)Chesney & Scott (1989)Melino & Turnbull (1990)Stein & Stein (1991)Hofmann, Pl.& Schweizer (1992)Heston (1993),. . .

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Empirical Evidence on Log-Returns

• Markowitz & Usmen (1996)

daily S&P500 → Studentt(4.5)

• Hurst & Platen (1997)

daily stock market indices→ Studentt(4)

• Fergusson& Pl. (2006), Pl.& Rendek (2008)

daily WSI, EWI104s with high accuracy→ Studentt(4)

• Breymann, Dias & Embrechts (2003)

copula of joint distribution of log-returns of exchange rates →Studentt copula with roughly four degrees of freedom

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−10 −5 0 5 10

10−4

10−3

10−2

10−1

Figure 4.6: Log-histogram of the EWI104s log-returns and Studentt density

with four degrees of freedom.c© Copyright Eckhard Platen 10 BA - Toronto C 4 132

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0

0.5

1

1.5

2

−5−4

−3−2.15

−10

1 2

34

5

−2.94

−2.92

−2.9

−2.88

−2.86

−2.84

αλ

Estimated λ

Estimated LLF

× 105

Figure 4.7: Log-likelihood function based on the EWI104s.

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Country Student-t NIG Hyperbolic VG ν

Australia 0.000000 76.770817 150.202282 181.632971 4.281222

Austria 0.000000 39.289103 77.505683 102.979330 4.725907

Belgium 0.000000 31.581622 60.867570 83.648470 4.989912

Brazil 2.617693 5.687078 63.800349 60.078395 2.713036

Canada 0.000000 47.506215 79.917741 104.297607 5.316154

Denmark 0.000000 41.509921 87.199686 114.853658 4.512101

Finland 0.000000 28.852844 68.677271 88.553080 4.305638

France 0.000000 26.303544 57.639325 80.567283 4.722787

Germany 0.000000 27.290205 52.667918 71.120798 5.005856

Greece 0.000000 60.432172 104.789463 125.601499 4.674626

Hong.Kong 0.000000 42.066531 100.834255 122.965326 3.930473

India 0.000000 74.773701 163.594078 198.002956 3.998713

Ireland 0.000000 77.727856 136.505582 170.013644 4.761519

Italy 0.000000 25.196598 55.185625 75.481897 4.668983

Japan 0.000000 37.630363 77.163656 102.967380 4.649745

Korea.S. 0.000000 120.904983 304.829431 329.854620 3.289204

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Malaysia 0.000000 79.714054 186.013963 221.061290 3.785195

Netherlands 0.000000 26.832761 51.625813 71.541627 5.084056

Norway 0.000000 42.243851 89.012090 115.059003 4.472349

Portugal 0.000000 61.177624 137.681039 165.689683 3.984860

Singapore 0.000000 36.379685 77.600590 98.124375 4.251472

Spain 0.000000 56.694545 109.533768 138.259224 4.517153

Sweden 0.000000 77.618384 143.420049 178.983373 4.546640

Taiwan 0.000000 41.162560 96.283628 115.186585 3.914719

Thailand 0.000000 78.250621 254.590254 267.508143 3.032038

UK 0.000000 26.693076 55.937248 80.678494 4.952843

USA 0.000000 40.678242 79.617362 100.901197 4.636661

Table 1:Ln test statistic of the EWI104s for different currency denominations

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Index Log-returns

• Student t distributed with about 4 degrees of freedom

• clustering

Find corresponding stationary volatility processes !

Kessler (1997), Prakasa Rao (1999)

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• normal mixing

log-return conditionally Gaussian distributed

with stochastic variance process

for small time step sizeh > 0

∆ ln(Sδ∗

t ) = ln

(

Sδ∗

t+h

Sδ∗

t

)

∼ N(

θ2t

2h, θ2

t h

)

whenθ2t has inverse gamma stationary density

=⇒ estimated log-return appears to be Studentt distributed

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A Class of Continuous Stochastic Volatility Models

• discounted NP

Sδ∗

t =Sδ∗

t

S0t

dSδ∗

t = Sδ∗

t (θ2t dt+ θt dWt)

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Particular Stochastic Volatility Models

• Hull and White’87 model

Hull & White (1987)

dθ2t = µ θ2

t dt+ ξ θ2t dWt

squared volatility does not have a stationary dynamics

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• Heston model

Hull & White (1988), Heston (1993)

mean reverting dynamics

k, θ andγ are positive constants

=⇒

dθ2t = k (θ2 − θ2

t ) dt+ γ |θt| dWt

θ20 > 0, κ

γ2 ≥ 12

=⇒ has as stationary density gamma density

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• Scott model

Scott (1987)

Stein & Stein (1991)

Ornstein-Uhlenbeck process

k, θ, γ positive constants

dθt = k (θ − θt) dt+ γ dWt

θ0 ∈ ℜ

=⇒ θ2t has as stationary density a gamma density

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• Wiggins model

Wiggins (1987)

Chesney & Scott (1989)

Melino & Turnbull (1990)

d ln(θt) = k(

ln(θ) − ln(θt))

dt+ γ dWt

θ0 > 0

θ2t has as stationary density a log-normal density

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• inverted gamma distribution

pθ2(y) =(12ν)

12 ν

ε2 Γ(12ν)

(

y

ε2

)− 12 ν−1

exp

−12ν ε2

y

y > 0, degrees of freedomν > 0, scaling parameterε

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• SDE for squared volatility

dθ2t = k θ

4(ξ−1)t (θ2 − θ2

t ) dt+ γ θ2 ξt dWt

degree of freedom

ν =2 (2 ξ − 1)

1 − ε2

θ2

=⇒ stationary density inverted gamma

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•32

volatility model

ξ = 32

Pl. (1997), Lewis (2000), Pl. (2001)

dθ2t = k θ2

t (θ2 − θ2t ) dt+ γ θ3

t dWt

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• ARCH diffusion

ξ = 1

Engle (1982), Nelson (1990) and Frey (1997)

dθ2t = k (θ2 − θ2

t ) dt+ γ θ2t dWt

continuous time limit of innovation process

GARCH(1,1) and NGARCH(1,1)

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Implied Volatilities for the ARCH Diffusion Model

Hurst (1997), Lewis (2000), Heath, Hurst& Pl. (2001)

GARCH(1,1) of Bollerslev (1986) whenW andW are independent

continuous time limit of NGARCH(1, 1) model of Engle & Ng (1993)

two-factor model

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80

90

100

110

120K 0.2

0.4

0.6

0.8

1

T

0.2

0.21

0.22

80

90

100

110

120K

Figure 4.8: Implied volatility surface for zero correlation.

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80

90

100

110

120K -0.4

-0.2

0

0.2

0.4

rho

0.18

0.2

0.22

80

90

100

110

120K

Figure 4.9: Effect of changing correlation on implied volatilities.

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8090

100

110

120K

5

10

15

20

k

0.1950.1975

0.2

0.2025

0.205

8090

100

110

120K

Figure 4.10: Effect of changing speed of adjustment on implied volatilities.

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8090

100

110

120K

0.5

1

1.5

2

gamma

0.19

0.2

0.21

8090

100

110

120K

Figure 4.11: Effect of changing volatility of the squared volatility on implied

volatilities.

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Moneyness

Opt

ion

Pric

e D

iffer

ence

-0.3 -0.2 -0.1 0.0 0.1 0.2 0.3

-0.1

5-0

.10

-0.0

50.

00.

05

GLMRHestonBlack-Scholes

Figure 4.12: Option price differences between the ARCH diffusion (GLMR),

Heston and Black-Scholes models, with time to maturity of three months.

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Moneyness

Impl

ied

Vol

atili

ty

-0.3 -0.2 -0.1 0.0 0.1 0.2 0.3

0.14

0.16

0.18

0.20

GLMRHestonBlack-Scholes

Figure 4.13: Implied volatilities of the ARCH diffusion (GLMR), Heston

and Black-Scholes models, with time to maturity of three months.

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5 Minimal Market Model

• search for parsimonious one-factor model

• Diversification Theorem =⇒

well diversified stock market index approximates NP

• discounted NP

dSδ∗

t = Sδ∗

t |θt| (|θt| dt+ dWt),

where

dWt =1

|θt|d∑

k=1

θkt dW

kt

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0

10

20

30

40

50

60

70

80

90

100

1930 1940 1950 1960 1970 1980 1990 2000

time

Figure 5.1: Discounted S&P500 total return index.

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-2

-1

0

1

2

3

4

5

1930 1940 1950 1960 1970 1980 1990 2000

time

Figure 5.2: Logarithm of discounted S&P500.

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• logarithm of discounted NP

• is not a transformed Wiener process

• is not a process with independent increments

• has somefeedback effect

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Drift Parametrization

• discounted NP drift

αt = Sδ∗

t |θt|2

strictly positive, predictable

=⇒• volatility

|θt| =

αt

Sδ∗

t

leverage effect creates naturalfeedbackunder independent drift

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• discounted NP

dSδ∗

t = αt dt+

Sδ∗

t αt dWt

drift has economic meaning,

fundamental value

• transformed time

ϕt =1

4

∫ t

0

αs ds

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• squared Bessel process of dimension four

Xϕt= Sδ∗

t

dW (ϕt) =√αt dWt

dXϕ = 4 dϕ+ 2√

Xϕ dW (ϕ)

Revuz & Yor (1999)

economically founded dynamics inϕ-time

still no specific dynamics int-time

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Time Transformed Bessel Process

d

Sδ∗

t =3αt

8

Sδ∗

t

dt+1

2

√αt dWt

• quadratic variation

[√

Sδ∗

]

t=

1

4

∫ t

0

αs ds

• transformed time

ϕt =[√

Sδ∗

]

t

observable

c© Copyright Eckhard Platen 10 BA - Toronto C 5 161

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0

1

2

3

4

5

6

7

8

9

10

1930 1940 1950 1960 1970 1980 1990 2000

time

Figure 5.3: Empirical quadratic variation of the square rootof the discounted

NP.c© Copyright Eckhard Platen 10 BA - Toronto C 5 162

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Stylized Minimal Market Model

Pl. (2001, 2002, 2006)

• assumediscounted NP drift as

αt = α exp η t

• initial parameter α > 0

• net growth rate η

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• transformed time

ϕt =α

4

∫ t

0

exp η z dz

4 η(exp η t − 1)

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0

1

2

3

4

5

6

7

8

9

10

1930 1940 1950 1960 1970 1980 1990 2000

time

[sqrt(discounted index)]theoretical variation

Figure 5.4: Fitted and observed transformed time.

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• normalized NP

Yt =Sδ∗

t

αt

dYt = (1 − η Yt) dt+√

Yt dWt

square root process of dimension four

=⇒ parsimonious model, long term viability

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=⇒• discounted NP

Sδ∗

t = Yt αt

• NP

Sδ∗

t = S0t S

δ∗

t = S0t Yt αt

• scaling parameterα0 = 0.01468

• net growth rateη = 0.054

• reference level1η

= 18.5

• speed of adjustmentη

• half life time of major displacement ln(2)η

≈ 13 years

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0

10

20

30

40

50

60

70

80

90

1930 1940 1950 1960 1970 1980 1990 2000

time

Figure 5.5: Normalized NP.

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• logarithm of discounted NP

ln(Sδ∗

t ) = ln(Yt) + ln(α0) + η t

• no need for extra volatility process in MMM

• realistic long term dynamics

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Volatility of NP under the stylized MMM

|θt| =1√Yt

• squared volatility

d|θt|2 = d

(

1

Yt

)

= |θt|2 η dt− (|θt|2)

32 dWt

3/2 volatility model

Platen (1997), Lewis (2000)

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0.1

0.15

0.2

0.25

0.3

0.35

1930 1940 1950 1960 1970 1980 1990 2000

time

Figure 5.6: Volatility of the NP under the stylized MMM.

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Transition Density of Stylized MMM

• transition density ofdiscounted NP Sδ∗

p(s, x; t, y) =1

2 (ϕt − ϕs)

(

y

x

)12

exp

− x+ y

2 (ϕt − ϕs)

× I1

( √x y

ϕt − ϕs

)

ϕt =α

4 η(expη t − 1)

I1(·) modified Bessel function of the first kind

c© Copyright Eckhard Platen 10 BA - Toronto C 5 172

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• non-central chi-squaredistributed random variable:

y

ϕt − ϕs

=Sδ∗

t

ϕt − ϕs

with δ = 4 degrees of freedom andnon-centrality parameter:

x

ϕt − ϕs

=Sδ∗

s

ϕt − ϕs

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80

90

100

110

120

y0.1

0.2

0.3

0.4

0.5

t

0

0.05

0.1

0.15

80

90

100

110y

Figure 5.7: Transition density of squared Bessel process forδ = 4.

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Zero Coupon Bond under the stylized MMM

• zero coupon bond

P (t, T ) = Sδ∗

t Et

(

1

Sδ∗

T

)

= P ∗T (t)Et

(

Sδ∗

t

Sδ∗

T

)

with savings bond

P ∗T (t) = exp

−∫ T

t

rs ds

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δ = 4 =⇒

P (t, T ) = P ∗T (t)

(

1 − exp

− Sδ∗

t

2 (ϕT − ϕt)

)

< P ∗T (t)

for t ∈ [0, T ), Platen (2002)

with time transform

ϕt =α

4 η(expη t − 1)

P (0, T ) = 0.00077

P ∗T (0) = 0.0335

P (0,T )P ∗

T (0)≈ 0.023

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0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1930 1940 1950 1960 1970 1980 1990 2000

time

savings bondfair zero coupon bond

savings account

Figure 5.8: Savings bond, fair zero coupon bond and savings account.

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-8

-7

-6

-5

-4

-3

-2

-1

0

1

1930 1940 1950 1960 1970 1980 1990 2000

time

ln(savings bond)ln(fair zero coupon bond)

Figure 5.9: Logarithms of savings bond and fair zero coupon bond.

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Forward Rates under the MMM

• forward rate

f(t, T ) = − ∂

∂Tln(P (t, T ))

= rT + n(t, T )

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• market price of risk contribution

n(t, T ) = − ∂

∂Tln

(

1 − exp

− Sδ∗

t

2(ϕT − ϕt)

)

=1

(

exp

Sδ∗

t

2(ϕT −ϕt)

− 1)

Sδ∗

t

(ϕT − ϕt)2

αT

8

limT →∞

n(t, T ) = η

Pl. (2005a), Miller& Pl. (2005)

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0.020.04

0.06

0.08

0.1

eta

20

40

60

80

T

0

0.025

0.05

0.075

0.1

0.020.04

0.06

0.08eta

Figure 5.10: Market price of risk contribution in dependence on η andT .

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Free Snack from Savings Bond

• potential existence of weak form of arbitrage?

borrow amountP (0, T ) from savings account

Sδt = P (t, T ) − P (0, T ) expr t

such thatSδ0 = 0

SδT = 1 − P (0, T ) expr T > 0

lower bound

Sδt ≥ −P (0, T ) expr t

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• sinceSδt may become negative

allowed by strong arbitrage concept

• cheap thrills may exist

Loewenstein & Willard (2000)

MMM doesnot admit an equivalent risk neutral probability measure

=⇒there is afree lunch with vanishing risk

Delbaen & Schachermayer (2006)

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Absence of an Equivalent Risk Neutral Probability Measure

• fair zero coupon bond has a lower price than the savings bond

P (t, T ) < P ∗T (t) = exp

−∫ T

t

rs ds

=S0

t

S0T

• Radon-Nikodym derivative

Λt =S0

t

S00

=Sδ∗

0

Sδ∗

t

strict (A, P )-supermartingaleunder MMM

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0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

1930 1940 1950 1960 1970 1980 1990 2000

time

Radon-Nikodym derivativeTotal RN-Mass

Figure 5.11: Radon-Nikodym derivative and total mass of putative risk neu-

tral measure.c© Copyright Eckhard Platen 10 BA - Toronto C 5 185

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• hypothetical risk neutral measure

total mass:

Pθ,T (Ω) = E0 (ΛT ) = 1 − exp

− Sδ∗

0

2ϕT

< Λ0 = 1

Pθ is not a probability measure

c© Copyright Eckhard Platen 10 BA - Toronto C 5 186

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European Call Options under the MMM

real world pricing formula =⇒

cT,K(t, Sδ∗

t ) = Sδ∗

t Et

(

(Sδ∗

T −K)+

Sδ∗

T

)

= Et

(

Sδ∗

t − K Sδ∗

t

Sδ∗

T

)+

= Sδ∗

t

(

1 − χ2(d1; 4, ℓ2))

−K exp−r (T − t) (1 − χ2(d1; 0, ℓ2))

χ2(·; ·, ·) non-central chi-square distribution

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with

d1 =4 ηK exp−r (T − t)

S0t αt (expη (T − t) − 1)

and

ℓ2 =2 η Sδ∗

t

S0t αt (expη (T − t) − 1)

Hulley, Miller & Pl. (2005)

Hulley & Pl. (2008)

Miller & Pl. (2008)

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0.6

0.8

1

1.2K2

4

6

8

10

T

0.2

0.225

0.25

0.275

0.6

0.8

1

1.2K

Figure 5.12: Implied volatility surface for the stylized MMM.

c© Copyright Eckhard Platen 10 BA - Toronto C 5 189

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• implied volatility

in BS-formula adjust short rate to

r = − 1

T − tln(P (t, T ))

otherwise put and call implied volatilities do not match

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European Put Options under the MMM

• fair put-call parity relation

pT,K(t, Sδ∗

t ) = cT,K(t, Sδ∗

t ) − Sδ∗

t +K P (t, T )

• European put option formula

pT,K(t, Sδ∗

t ) = −Sδ∗

t

(

χ2(d1; 4, ℓ2))

+K exp−r (T − t)(χ2(d1; 0, ℓ2) − exp −ℓ2)

Hulley, Miller & Pl. (2005)

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• put-call paritybreaks down if one uses the savings bondP ∗T (t)

pT,K(t, Sδ∗

t ) < cT,K(t, Sδ∗

t ) − Sδ∗

t +K exp−r (T − t)

for t ∈ [0, T )

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• excellent hedge performance for extreme maturities

Hulley & Pl. (2008)

European calls

European puts

barrier options

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Comparison to Hypothetical Risk Neutral Prices

• hypothetical risk neutral price c∗T,K(t, Sδ∗

t )

of a European call option on the NP

• benchmarked hypothetical risk neutral call price

c∗T,K(t, Sδ∗

t ) =c∗

T,K(t, Sδ∗

t )

Sδ∗

t

local martingale

c∗T,K(·, ·) uniformly bounded

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=⇒ c∗T,K martingale =⇒

c∗T,K(t, Sδ∗

t ) = cT,K(t, Sδ∗

t )

=⇒c∗

T,K(t, Sδ∗

t ) = cT,K(t, Sδ∗

t )

c© Copyright Eckhard Platen 10 BA - Toronto C 5 195

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• hypothetical risk neutral put-call parity

p∗T,K(t, Sδ∗

t ) = c∗T,K(t, Sδ∗

t ) − Sδ∗

t +K P ∗T (t)

sinceP ∗T (t) > P (t, T ) =⇒

pT,K(t, Sδ∗

t ) < p∗T,K(t, Sδ∗

t )

t ∈ [0, T )

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Difference in Asymptotic Put Prices

• hypothetical risk neutral prices can become extreme if NP value tends

towards zero

• asymptotic fair zero coupon bond

limS

δ∗

t →0PT (t, T )

a.s.= 0

for t ∈ [0, T )

• asymptotic fair European call

limS

δ∗

t →0cT,K(t, Sδ∗

t )a.s.= lim

Sδ∗

t →0Sδ∗

t cT,K(t, Sδ∗

t ) = 0

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• asymptotic fair putfair put-call parity =⇒

limS

δ∗

t →0pT,K(t, Sδ∗

t )a.s.= 0

• asymptotic hypothetical risk neutral puthypothetical risk neutral put-call parity =⇒

limS

δ∗

t →0p∗

T,K(t, Sδ∗

t )

a.s.= lim

Sδ∗

t →0

(

pT,K(t, Sδ∗

t ) +KS0

t

S0T

exp

− Sδ∗

t

2(ϕT − ϕt)

)

a.s.= K

S0t

S0T

> 0

dramatic differences can arise

c© Copyright Eckhard Platen 10 BA - Toronto C 5 198

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0

2

4

6

8

1930 1940 1950 1960 1970 1980 1990 2000

time

ln(K*savings bond)ln(risk neutral put)

ln(put)

Figure 5.13: Logarithms of savings bond timesK, risk neutral put and fair

put.c© Copyright Eckhard Platen 10 BA - Toronto C 5 199

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MMM with Random Market Activity

• squared Bessel process with dimensionδ = 4

Sδ∗ = Sδ∗

t , t ∈ [0,∞)

dSδ∗

t = αt dt+

αt Sδ∗

t dWt

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• NP

Sδ∗

t = S0t S

δ∗

t

• volatility

|θt| =

αt

Sδ∗

t

• discounted NP drift

αt to be modeled

c© Copyright Eckhard Platen 10 BA - Toronto C 5 201

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0.6

0.8

1

1.2K2

4

6

8

10

T

0.2

0.225

0.25

0.275

0.6

0.8

1

1.2K

Figure 5.14: Implied volatility surface for the stylized MMM.

c© Copyright Eckhard Platen 10 BA - Toronto C 5 202

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0.5

0.75

1

1.25

1.5

KS

0.20.4

0.60.8

11.2

1.41.6T

0.22

0.24

0.26

0.28

0.5

0.75

1

1.25KS

0.20.4

0.60.8

11.2

1.4

Figure 5.15: Average S&P500 implied volatility surface.

c© Copyright Eckhard Platen 10 BA - Toronto C 5 203

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100

200

300

time 0.6

0.8

1

1.2

1.4

moneyness

20

40

60

100

200

300

time

Figure 5.16: Implied volatilities for S&P500 three month options.

c© Copyright Eckhard Platen 10 BA - Toronto C 5 204

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100

200

300

time 0.6

0.8

1

1.2

1.4

moneyness

1020304050

100

200

300

time

Figure 5.17: Implied volatilities for S&P500 one year options.

c© Copyright Eckhard Platen 10 BA - Toronto C 5 205

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• market activity mt

Breymann, Kelly& Pl. (2006)

Pl. & Rendek (2008)

αt = ξtmt

with

ξt = ξ0 exp η t

dmt = k(mt)β2 dt+ βmt

(

dWt +√

1 − 2 dWt

)

- correlation parameter

activity volatility β > 0

W - independent Wiener process

c© Copyright Eckhard Platen 10 BA - Toronto C 5 206

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Example:

• drift

k(mt) = (p− gmt)mt

2

• stationary density

pm(y) =gp−1

Γ(p− 1)yp−2 exp−g y

gamma density with meanp−1g

and variance1g

for p > 1 andg > 0

c© Copyright Eckhard Platen 10 BA - Toronto C 5 207

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0.5

1

1.5y

10

20

30

40

50

g

0

1

2

0.5

1

1.5y

Figure 5.18: Stationary density of market activitymt = y as function ofy

and speed of adjustment parameterg.c© Copyright Eckhard Platen 10 BA - Toronto C 5 208

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Zero Coupon Bond

• benchmarked zero coupon bond

PT (t, Sδ∗

t ,mt) = Et

(

1

Sδ∗

T

)

= Et

(

1

S0T S

δ∗

T

)

• zero coupon bond

PT (t, Sδ∗

t ,mt) = Sδ∗

t PT (t, Sδ∗

t ,mt) = S0t S

δ∗

t PT (t, Sδ∗

t ,mt)

c© Copyright Eckhard Platen 10 BA - Toronto C 5 209

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European Options on a Market Index

• put option price

pT,K(t, Sδ∗

t ,mt) = S0t S

δ∗

t Et

(

K

S0T S

δ∗

T

− 1

)+

effect of random market time on implied volatilities

curvature for the short dated implied volatility surface

Heath& Pl. (2005a)

c© Copyright Eckhard Platen 10 BA - Toronto C 5 210

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80

90

100

110

120

K 0.2

0.4

0.6

0.8

1

T

0.30.32

0.34

0.36

80

90

100

110K

Figure 5.19: Implied volatilities for put options on index asa function of

strikeK and maturityT .c© Copyright Eckhard Platen 10 BA - Toronto C 5 211

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80

90

100

110

120

K

2

4

6

8

10

g

0.3

0.32

0.34

80

90

100

110K

Figure 5.20: Implied volatilities for put options as a function of strikeK and

speed of adjustmentg.

c© Copyright Eckhard Platen 10 BA - Toronto C 5 212

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80

100

120K 2

4

6

8

10

T

0.30.3250.35

0.375

0.4

80

100

120K

Figure 5.21: Implied volatilities for long dated put optionsas a function of

strikeK and maturityT .

c© Copyright Eckhard Platen 10 BA - Toronto C 5 213

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6 Stylized Multi-Currency MMM

Pl. (2001)

Heath& Pl. (2005a)

d+ 1 currencies

Sδ∗

i (t) NP in ith currency

rit - ith short rate

θki (t) - market price of risk

Sδ∗

i (t) = αit Y

it S

ii(t)

c© Copyright Eckhard Platen 10 BA - Toronto C 6 214

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αit = αi

0 expηi t

Sii(t) = expri t

• ith normalized NP

dY it =

(

1 − ηi Y it

)

dt+

Y it

d+1∑

k=1

qi,k dW kt

scaling levelsqi,k

d+1∑

k=1

(qi,k)2 = 1

c© Copyright Eckhard Platen 10 BA - Toronto C 6 215

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• (i, j)th exchange rate

Xi,jt =

Sδ∗

i (t)

Sδ∗

j (t)=Y i

t αit S

ii(t)

Y jt α

jt S

jj (t)

dXi,jt = Xi,j

t

(ri − rj) dt+

d+1∑

k=1

qi,k

Y it

− qj,k

Y jt

(

qi,k

Y it

dt+ dW kt

)

c© Copyright Eckhard Platen 10 BA - Toronto C 6 216

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• jth savings account inith currency

Sji (t) = Xi,j

t Sjj (t)

dSji (t) = Sj

i (t)

ri dt+

d+1∑

k=1

qi,k

Y it

− qj,k

Y jt

(

qi,k

Y it

dt+ dW kt

)

c© Copyright Eckhard Platen 10 BA - Toronto C 6 217

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• stochastic market price of risk

θki (t) =

qi,k

Y it

• (j, k)th volatility

bj,ki (t) = θk

i (t) − θkj (t)

equity prices

commodity prices

c© Copyright Eckhard Platen 10 BA - Toronto C 6 218

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7 Valuing Guaranteed Minimum Death Benefits

• variable annuitiesfund-linked

tax-deferred

guarantees

• guaranteed minimum death benefits(GMDBs)

roll-ups:

original investment accrued at a pre-defined interest rate

ratchets:

death benefit based upon the highest anniversary account value

embedded options:

hedging against market downturn occurrence of death

c© Copyright Eckhard Platen 10 BA - Toronto C 7 219

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• GMDB put, floating put and/or look-back put option

long maturities of contracts

standard option pricing theory ?

no obvious best choice for price:

IFRS Phase II

CFO-Forum (2008)

CRO-Forum (2008)

Solvency II

Verheugen & Hines (2008)

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• pricing and hedging of GMDBs

benchmark approachin

Pl. (2002, 2004b), Pl.& Heath (2006)

Buhlmann& Pl. (2003)

best performing portfolio isbenchmark

doesnot require

existence of an equivalent risk neutral probability measure

uniquefair price is theminimal price

may provide significantly lower prices

c© Copyright Eckhard Platen 10 BA - Toronto C 7 221

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Financial Model

• underlying risky security (unit)

dSt = (µt − γ)Stdt+ σtSt dWt

γ ≥ 0 management fee rates

Wt - Brownian motion

• savings account

dBt = rtBt dt

c© Copyright Eckhard Platen 10 BA - Toronto C 7 222

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• market price of risk

θt =µt − γ − rt

σt

• risky asset

dSt

St

= rt dt+ σtθt dt+ σt dWt

c© Copyright Eckhard Platen 10 BA - Toronto C 7 223

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• self-financing portfolio

Vt = δ0tBt + δ1tSt

dVt = δ0t dBt + δ1t dSt

• fractions

π0t = δ0t

Bt

Vt

, π1t = δ1t

St

Vt

π0t + π1

t = 1

c© Copyright Eckhard Platen 10 BA - Toronto C 7 224

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• instantaneous portfolio return

dVt

Vt

= π0t

dBt

Bt

+ π1t

dSt

St

= rt dt+ π1tσt(θt dt+ dWt)

c© Copyright Eckhard Platen 10 BA - Toronto C 7 225

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• numeraire portfolio (NP) as benchmark

Long (1990)

V ∗ is best performing in several ways

• is growth optimal portfolio

Kelly (1956)

V ∗ = maxE(log VT )

π1∗t =

µt − γ − rt

σ2t

=θt

σt

dV ∗t

V ∗t

= rt dt+ θt(θt dt+ dWt)

Merton (1992)

c© Copyright Eckhard Platen 10 BA - Toronto C 7 226

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• NP best performing portfolio

lim supT →∞

1

Tlog

(

V ∗T

V ∗0

)

≥ lim supT →∞

1

Tlog

(

VT

V0

)

global well diversified index≈ NP

Pl. (2005b)

c© Copyright Eckhard Platen 10 BA - Toronto C 7 227

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0

10

20

30

40

50

60

70

80

90

100

1930 1940 1950 1960 1970 1980 1990 2000

time

Figure 7.1: Discounted S&P500 total return index.

c© Copyright Eckhard Platen 10 BA - Toronto C 7 228

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-2

-1

0

1

2

3

4

5

1930 1940 1950 1960 1970 1980 1990 2000

time

Figure 7.2: Logarithm of discounted S&P500.

c© Copyright Eckhard Platen 10 BA - Toronto C 7 229

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• benchmarked price

Ut = Ut

V ∗

t

U nonnegative =⇒

Ut ≥ Et

(

Us

)

t ≤ s

supermartingales (no upward trend)

Pl. (2002)

no strong arbitrage

c© Copyright Eckhard Platen 10 BA - Toronto C 7 230

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• benchmarked securities that form martingales are calledfair.

Ut = Et

(

Us

)

t ≤ s

c© Copyright Eckhard Platen 10 BA - Toronto C 7 231

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• Law of the Minimal Price

Pl. (2008)

Fair prices are minimal prices

V nonnegative fair portfolio

V ′ nonnegative portfolio

VT = V ′T

supermartingale property

=⇒Vt ≤ V ′

t

t ∈ [0, T ],

c© Copyright Eckhard Platen 10 BA - Toronto C 7 232

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0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

1930 1940 1950 1960 1970 1980 1990 2000

time

benchmarked savings bondbenchmarked fair zero coupon bond

Figure 7.3: Benchmarked savings bond and benchmarked fair zero coupon

bond.c© Copyright Eckhard Platen 10 BA - Toronto C 7 233

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• real world pricing formulafor

Et

(

HT

V ∗T

)

< ∞

UH(t) = V ∗t Et

(

HT

V ∗T

)

t ∈ [0, T ]

no risk neutral probability needs to exist

c© Copyright Eckhard Platen 10 BA - Toronto C 7 234

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• actuarial pricing formula

whenHT is independent ofV ∗T

=⇒UH(t) = P (t, T )Et(HT )

zero coupon bond

P (t, T ) = V ∗t Et

(

1

V ∗T

)

c© Copyright Eckhard Platen 10 BA - Toronto C 7 235

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• standard risk neutral pricing

Ross (1976), Harrison & Pliska (1983)

complete market

candidate Radon-Nikodym derivative

Λt =dQ

dP

At

=BtV

∗0

B0V∗

t

supermartingale =⇒

1 = Λ0 ≥ E0 (ΛT )

c© Copyright Eckhard Platen 10 BA - Toronto C 7 236

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=⇒

UH(0) = E

(

V ∗0

V ∗T

HT

)

= E

(

ΛT

B0

BT

HT

)

≤E(

ΛTB0

BTHT

)

E(ΛT )

c© Copyright Eckhard Platen 10 BA - Toronto C 7 237

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Only in the special case whenΛT martingale

=⇒ risk neutral pricing formula:

UH(0) = EQ

(

B0

BT

HT

)

Ignores any real trend !

c© Copyright Eckhard Platen 10 BA - Toronto C 7 238

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• Trends ignored also when using:

stochastic discount factor, Cochrane (2001);

deflator, Duffie (2001);

pricing kernel , Constantinides (1992);

state price density, Ingersoll (1987);

NP as Long (1990)

c© Copyright Eckhard Platen 10 BA - Toronto C 7 239

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• Example zero coupon bond

benchmarked fair zero coupon

P (t, T ) =P (t, T )

V ∗t

= Et

(

1

V ∗T

)

martingale (no trend)

for rt - deterministic

P (t, T ) = V ∗t Et

(

1

V ∗T

)

= exp

−T∫

t

rs ds

Et

(

V ∗t

V ∗T

)

,

V ∗t =

V ∗

t

Bt- discounted NP

c© Copyright Eckhard Platen 10 BA - Toronto C 7 240

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0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

1930 1940 1950 1960 1970 1980 1990 2000

time

benchmarked savings bondbenchmarked fair zero coupon bond

Figure 7.4: Benchmarked savings bond and benchmarked fair zero coupon

bond.c© Copyright Eckhard Platen 10 BA - Toronto C 7 241

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=⇒ downward trend reflects equity premium

=⇒ Λ strict supermartingale (downward trend), then

P (t, T ) < exp

−T∫

t

rs ds

=Bt

BT

c© Copyright Eckhard Platen 10 BA - Toronto C 7 242

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0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

1930 1940 1950 1960 1970 1980 1990 2000

time

Radon-Nikodym derivativeTotal RN-Mass

Figure 7.5: Radon-Nikodym derivative and total mass of putative risk neutral

measure.c© Copyright Eckhard Platen 10 BA - Toronto C 7 243

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0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1930 1940 1950 1960 1970 1980 1990 2000

time

savings bondfair zero coupon bond

savings account

Figure 7.6: Savings bond, fair zero coupon bond and savings account.

c© Copyright Eckhard Platen 10 BA - Toronto C 7 244

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-8

-7

-6

-5

-4

-3

-2

-1

0

1

1930 1940 1950 1960 1970 1980 1990 2000

time

ln(savings bond)ln(fair zero coupon bond)

Figure 7.7: Logarithms of savings bond and fair zero coupon bond.

c© Copyright Eckhard Platen 10 BA - Toronto C 7 245

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-2

-1

0

1

2

3

4

5

1930 1940 1950 1960 1970 1980 1990 2000

time

Figure 7.8: Logarithm of discounted S&P500.

c© Copyright Eckhard Platen 10 BA - Toronto C 7 246

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• discounted NP

V ∗t =

V ∗t

Bt

dV ∗t = V ∗

t θt (θt dt+ dWt)

= αt dt+

αt V∗

t dWt

c© Copyright Eckhard Platen 10 BA - Toronto C 7 247

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• discounted NP drift

αt := V ∗t θ

2t

=⇒ volatility

θt =

αt

V ∗t

reflects leverage effect

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• minimal market model

Pl. (2001, 2002)

MMM

discounted NP drift

assume

αt = α0 expηt

α0 > 0

net growth rateη > 0

=⇒ MMM

c© Copyright Eckhard Platen 10 BA - Toronto C 7 249

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-2

-1

0

1

2

3

4

5

1930 1940 1950 1960 1970 1980 1990 2000

time

ln(discounted index)trendline

Figure 7.9: Logarithm of discounted S&P500 and trendline.

c© Copyright Eckhard Platen 10 BA - Toronto C 7 250

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• normalized NP

Yt =V ∗

t

αt

dYt = (1 − ηYt) dt+√

Yt dWt

square root process of dimension four

Only one parameter !

c© Copyright Eckhard Platen 10 BA - Toronto C 7 251

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• volatility of NP

θt =1√Yt

=

αt

V ∗t

c© Copyright Eckhard Platen 10 BA - Toronto C 7 252

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• Zero coupon bond under the MMM

rt - deterministic

P (t, T ) = exp

−T∫

t

rs ds

(

1 − exp

− V ∗t

2(ϕ(T ) − ϕ(t))

)

Explicit formula !

c© Copyright Eckhard Platen 10 BA - Toronto C 7 253

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-8

-7

-6

-5

-4

-3

-2

-1

0

1

1930 1940 1950 1960 1970 1980 1990 2000

time

ln(savings bond)ln(fair zero coupon bond)

Figure 7.10: Logarithms of savings bond and fair zero coupon bond.

c© Copyright Eckhard Platen 10 BA - Toronto C 7 254

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0

0.2

0.4

0.6

0.8

1

1930 1940 1950 1960 1970 1980 1990 2000

time

Figure 7.11: Fraction invested in the savings account.

c© Copyright Eckhard Platen 10 BA - Toronto C 7 255

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-2e-005

-1e-005

0

1e-005

2e-005

3e-005

4e-005

5e-005

6e-005

7e-005

1930 1940 1950 1960 1970 1980 1990 2000

time

Figure 7.12: Benchmarked profit and loss.

c© Copyright Eckhard Platen 10 BA - Toronto C 7 256

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since

Et

(

ΛT

Λt

)

= Et

(

V ∗t

V ∗T

)

=

(

1 − exp

− V ∗t

2(ϕ(T ) − ϕ(t))

)

=⇒ P (t, T ) < Bt

BT

Overpricing by savings bond

no equivalent risk neutral probability measure

c© Copyright Eckhard Platen 10 BA - Toronto C 7 257

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0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

1930 1940 1950 1960 1970 1980 1990 2000

time

Radon-Nikodym derivativeTotal RN-Mass

Figure 7.13: Radon-Nikodym derivative and total mass of putative risk neu-

tral measure.c© Copyright Eckhard Platen 10 BA - Toronto C 7 258

Page 261: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

• European put option under the MMM

Hulley, Miller & Pl. (2005)

p(t, V ∗t , T,K, r) = V ∗

t Et

(

(K − V ∗τ )+

V ∗τ

)

p(t, V ∗t , T,K, r) = −V ∗

t χ2(d1; 4, l2)

+Ke−r(T −t)(

χ2(d1; 0, l2) − exp −l2/2)

c© Copyright Eckhard Platen 10 BA - Toronto C 7 259

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with

d1 =4ηK exp−r(T − t)

Btαt(expη(T − t) − 1)

and

l2 =4ηV ∗

t

Btαt(expη(T − t) − 1)

c© Copyright Eckhard Platen 10 BA - Toronto C 7 260

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χ2(x;n, l) non-central chi-square distribution function

n ≥ 0 degrees of freedom

non-centrality parameterl > 0

χ2(x;n, l) =

∞∑

k=0

exp− l

2

(

l2

)k

k!

1 −Γ(

x2; n+2k

2

)

Γ(

n+2k2

)

c© Copyright Eckhard Platen 10 BA - Toronto C 7 261

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• putative risk neutral price

p(t, V ∗t , T,K, r) = p(t, V ∗

t , T,K, r)+Ke−r(T −t) exp

− V ∗t

2(ϕ(T ) − ϕ(t))

risk neutral is overpricing

for V ∗t → 0 =⇒ p(t, V ∗

t , T,K, r) → 0

and

p(t, V ∗t , T,K, r) → K e−r(T −t) > 0

risk neutral ignores trends

c© Copyright Eckhard Platen 10 BA - Toronto C 7 262

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0

2

4

6

8

1930 1940 1950 1960 1970 1980 1990 2000

time

ln(K*savings bond)ln(risk neutral put)

ln(put)

Figure 7.14: Logarithms of savings bond timesK, risk neutral put and fair

put.c© Copyright Eckhard Platen 10 BA - Toronto C 7 263

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Guaranteed Minimum Death Benefit (GMDB)

• payout to the policyholder

max(egτV0, Vτ )

time of deathτ

g ≥ 0 is the guaranteed instantaneous growth rate

V0 is the initial account value

Vτ is the unit value of the policyholder’s account at time of death τ

c© Copyright Eckhard Platen 10 BA - Toronto C 7 264

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• insurance chargesξ ≥ 0

=⇒ policyholder’s unit value

Vt = e−ξtV ∗t

=⇒

max(egτV0, Vτ ) = max(egτV0, e−ξτV ∗

τ )

= e−ξτ max(e(g+ξ)τV0, V∗

τ )

c© Copyright Eckhard Platen 10 BA - Toronto C 7 265

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insurance company invests the entire fund valueV in the NP V ∗

=⇒ payoff

HT = GMDBT = e−ξT[

(e(g+ξ)TV ∗0 − V ∗

T )+ + V ∗T

]

c© Copyright Eckhard Platen 10 BA - Toronto C 7 266

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fair valueGMDB0 of the total claim

real world pricing formula

GMDB0 = V ∗0 E

(

GMDBT

V ∗T

)

= e−ξT(

p(0, V ∗0 , T, e

(g+ξ)TV ∗0 , r) + V ∗

0

)

c© Copyright Eckhard Platen 10 BA - Toronto C 7 267

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0 5 10 15 20 25 300.8

0.85

0.9

0.95

1

1.05

1.1

MMM

T

GM

DB

0

0 5 10 15 20 25 300.8

0.85

0.9

0.95

1

1.05

1.1

risk neutral

T

GM

DB

0

0 5 10 15 20 25 300.8

0.85

0.9

0.95

1

1.05

1.1

1.15Black Scholes

T

GM

DB

0

0 5 10 15 20 25 300.9

0.95

1

1.05

1.1

1.15MMM

T

GM

DB

0

0 5 10 15 20 25 300.9

0.95

1

1.05

1.1

1.15risk neutral

T

GM

DB

0

0 5 10 15 20 25 300.9

0.95

1

1.05

1.1

1.15Black Scholes

T

GM

DB

0g=0.025

g=0

g=0.025g=0.025

g=0g=0

Figure 7.15:Present value of the GMDB under the real world pricing formula (left),

the risk neutral pricing formula (middle) and the Black Scholes formula (right) for

η = 0.05,α0 = 0.05, r = 0.05, ξ = 0.01 andY0 = 20.

c© Copyright Eckhard Platen 10 BA - Toronto C 7 268

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• lifetime τ is stochastic

GMDB0 = V ∗0 E

(

E

(

GMDBτ

V ∗τ

))

GMDB0 =

∫ T

0

(

p(0, V ∗0 , t, e

(g+ξ)tV ∗0 , r) + V ∗

0

)

e−ξtfτ (t) dt

fτ (·) - mortality density

c© Copyright Eckhard Platen 10 BA - Toronto C 7 269

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0 20 40 60 80 100 12010

−5

10−4

10−3

10−2

10−1

100

Age x

log(

q x)

malefemale

Figure 7.16: German mortality data

c© Copyright Eckhard Platen 10 BA - Toronto C 7 270

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rational investors will lapse when embedded put-option outof the moneyGMDBs have stochastic maturityTitanic options, Milevsky & Posner (2001)

• roll-up GMDB payoff

Ht =

(1 − βt)V∗

t , if lapsed at timet,

max(egτV0, V∗

τ ), if death occurs at timet = τ

surrender chargeβt

βt =

(8 − ⌈t⌉)%, t ≤ 7,

0, t > 7

no credit riskno accumulation phase

c© Copyright Eckhard Platen 10 BA - Toronto C 7 271

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20 30 40 50 60 70 801

1.05

1.1

1.15

Age x

GM

DB

0

malefemale

Figure 7.17: Value of the GMDB under the MMM for male and female pol-

icyholders agedx, assuming an irrational lapsation ofl = 1%.

c© Copyright Eckhard Platen 10 BA - Toronto C 7 272

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8 Markets with Event Risk

Jump Diffusion Markets

• filtered probability space(Ω,A,A, P )

• continuous trading uncertainty

m ∈ 1, 2, . . . , d

Wiener processesW k = W kt , t ∈ [0,∞), k ∈ 1, 2, . . . ,m

c© Copyright Eckhard Platen 10 BA - Toronto C 8 273

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• events

counting processpk = pkt , t ∈ [0,∞)

intensity hk = hkt , t ∈ [0,∞)

hkt > 0

∫ t

0

hks ds < ∞

• jump martingale

dqkt =

(

dpkt − hk

t dt) (

hkt

)− 12

k ∈ 1, 2, . . . , d−m

c© Copyright Eckhard Platen 10 BA - Toronto C 8 274

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E

(

(

qkt+∆ − qk

t

)2 ∣∣

∣At

)

= ∆

• trading uncertainty

W = W t = (W 1t , . . . , W

mt , q1

t , . . . , qd−mt )⊤, t ∈ [0,∞)

c© Copyright Eckhard Platen 10 BA - Toronto C 8 275

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Primary Security Accounts

dSjt = Sj

t−

(

ajt dt+

d∑

k=1

bj,kt dW k

t

)

j ∈ 1, 2, . . . , d

c© Copyright Eckhard Platen 10 BA - Toronto C 8 276

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Assumption 8.1

bj,kt ≥ −

hk−mt

for all t ∈ [0,∞), j ∈ 1, 2, . . . , d andk ∈ m+ 1, . . . , d.

Assumption 8.2 bt is invertible

c© Copyright Eckhard Platen 10 BA - Toronto C 8 277

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• market price of risk

θt = (θ1t , . . . , θ

dt )⊤ = b−1

t [at − rt 1]

at = (a1t , . . . , a

dt )

1 = (1, . . . , 1)⊤

=⇒

dSjt = Sj

t−

(

rt dt+

d∑

k=1

bj,kt (θk

t dt+ dW kt )

)

j ∈ 0, 1, . . . , d

c© Copyright Eckhard Platen 10 BA - Toronto C 8 278

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• strategy

δ = δt = (δ0t , . . . , δdt )⊤, t ∈ [0,∞)

• portfolio

Sδt =

d∑

j=0

δjt S

jt

• self-financing if

dSδt =

d∑

j=0

δjt dS

jt

c© Copyright Eckhard Platen 10 BA - Toronto C 8 279

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Growth Optimal Portfolio

• fraction

πjδ,t = δj

t

Sjt

Sδt

πδ,t = (π1δ,t, . . . , π

dδ,t)

dSδt = Sδ

t−

rt dt+ π⊤δ,t− bt (θt dt+ dW t)

strictly positive ⇐⇒

d∑

j=1

πjδ,t b

j,kt > −

hk−mt

k ∈ m+ 1, . . . , d

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d ln(Sδt ) = gδ

t dt+

m∑

k=1

d∑

j=1

πjδ,t b

j,kt dW k

t

+d∑

k=m+1

ln

1 +d∑

j=1

πjδ,t−

bj,kt

hk−mt

hk−mt dW k

t

• growth rate

gδt = rt +

m∑

k=1

d∑

j=1

πjδ,t b

j,kt θk

t − 1

2

d∑

j=1

πjδ,t b

j,kt

2

+

d∑

k=m+1

d∑

j=1

πjδ,tb

j,kt

(

θkt −

hk−mt

)

+ln

1+

d∑

j=1

πjδ,t

bj,kt

hk−mt

hk−mt

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Assumption 8.3√

hk−mt > θk

t

k ∈ m+ 1, . . . , d

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• fractions of candidate benchmark

πδ∗,t = (π1δ∗,t, . . . , π

dδ∗,t)

⊤ =(

c⊤t b

−1t

)⊤

ckt =

θkt for k ∈ 1, 2, . . . ,m

θkt

1−θkt (h

k−mt )−

12

for k ∈ m+ 1, . . . , d

if θkt

hk−mt

≪ 1

=⇒ ckt ≈ θk

t

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• candidate benchmark

dSδ∗

t = Sδ∗

t−(

rt dt+ c⊤t (θt dt+ dW t)

)

= Sδ∗

t−

(

rt dt+

m∑

k=1

θkt (θk

t dt+ dW kt )

+

d∑

k=m+1

θkt

1 − θkt (hk−m

t )− 12

(θkt dt+ dW k

t )

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Definition 8.4 Sδ ∈ V+ NP if gδt ≤ g

δt for all Sδ ∈ V+.

=⇒

Sδ∗ is a NP.

=⇒

gδ∗

t = rt+1

2

m∑

k=1

(θkt )2−

d∑

k=m+1

hk−mt

ln

1 +θk

t√

hk−mt − θk

t

+θk

t√

hk−mt

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for θkt

hk−mt

≪ 1 asymptotically

gδ∗

t ≈ rt +1

2

d∑

k=1

(θkt )2 = rt +

|θt|22

d ln(Sδ∗

t ) ≈ gδ∗

t dt+

d∑

k=1

θkt dW

kt

dSδ∗

t ≈ Sδ∗

t

(

rt +

d∑

k=1

θkt

(

θkt dt+ dW k

t

)

)

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• jump diffusion market (JDM) SJD(d) = S, a, b,~r, h,A, P

• benchmarked portfolio

Sδt =

Sδt

Sδ∗

t

dSδt =

m∑

k=1

d∑

j=1

δjt S

jt b

j,kt − Sδ

t θkt

dW kt

+

d∑

k=m+1

d∑

j=1

δjt S

jt− b

j,kt

1 − θkt

hk−mt

− Sδt− θ

kt

dW kt

driftless

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• benchmarked savings account

dS0t = −S0

t−

d∑

k=1

θkt dW

kt

driftless

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benchmarked portfolioSδ driftless =⇒ (A, P )-local martingale

Ansel & Stricker (1994)

=⇒

Theorem 8.5 In a JDM a nonnegativeSδ is an (A, P )-supermartin-

gale

Sδt ≥ E

(

Sδτ

∣At

)

τ ∈ [0,∞) andt ∈ [0, τ ].

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A nonnegative portfolio is a strongarbitrage if it can get out of zero.

Corollary 8.6

A JDM does not allow nonnegative portfolios that permit strong arbitrage.

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Law of the Minimal Price

Corollary 8.7 Aτ -measurable payoffH withE( H

Sδ∗

τ

|A0) < ∞. If

there exists a fair nonnegative portfolioSδ that replicates the payoff

Sδτ = H,

then this is the minimal nonnegative replicating portfolio.

=⇒• fair portfolios provide the cheapest hedge

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H Aτ -measurable payoff, withE( H

Sδ∗

τ

) < ∞

=⇒

real world pricing formula

UH(t) = Sδ∗

t E

(

H

Sδ∗

τ

At

)

• equivalent to riskneutral pricing as long as candidate Radon-Nikodym

derivative S0t

S00

forms(A, P )-martingale

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• zero coupon bond

P (t, T ) = E

(

Sδ∗

t

Sδ∗

T

At

)

• benchmarked zero coupon bond

P (t, T ) = P (t,T )

Sδ∗

t

dP (t, T ) = −P (t−, T )

d∑

k=1

σk(t, T ) dW kt

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=⇒

ln(P (t, T )) = ln(P (0, T )) −m∑

k=1

(∫ t

0

σk(s, T )dW ks +

1

2

∫ t

0

(σk(s, T ))2 ds

)

+

d∑

k=m+1

(

∫ t

0

σk(s, T )√

hk−ms ds+

∫ t

0

ln

(

1 − σk(s, T )√

hk−ms

)

dpks

)

c© Copyright Eckhard Platen 10 BA - Toronto C 8 294

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• forward rate

f(t, T ) = − ∂

∂Tln(P (t, T )) = − ∂

∂Tln(P (t, T ))

=⇒• forward rate equation

f(t, T ) = f(0, T ) +

m∑

k=1

∫ t

0

(

∂Tσk(s, T )

)

(

σk(s, T ) ds+ dW ks

)

+

d∑

k=m+1

∫ t

0

1

1 − σk(s,T )√h

k−ms

∂Tσk(s, T )

(

σk(s, T ) ds+ dW ks

)

similar to HJM equation

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Sequences of Diversified Portfolios

Sequence(Sδ(d))d∈N is a sequence of DPs if

∣πj

δ,t

∣≤ K2

d12+K1

for all j ∈ 0, 1, . . . , d, t ∈ [0,∞) and d ∈ d0, d0 + 1, . . ..

c© Copyright Eckhard Platen 10 BA - Toronto C 8 296

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• benchmarked primary security account

dSj

(d)(t) = −Sj

(d)(t−)

d∑

k=1

σj,k

(d)(t) dWkt

• kth total specific volatility

σk(d)(t) =

d∑

j=0

|σj,k

(d)(t)|

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Sequence of JDMsregular if

E

(

(

σk(d)(t)

)2)

≤ K5

for all t ∈ [0,∞), d ∈ N and k ∈ 1, 2, . . . , d.

c© Copyright Eckhard Platen 10 BA - Toronto C 8 298

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Sequence of Approximate NPs

• tracking rate

Rδ(d)(t) =

d∑

k=1

d∑

j=0

πjδ,t σ

j,k

(d)(t)

2

Sδ(d) is NP ⇐⇒ Sδ

(d) ≡ constant

⇐⇒Rδ

(d)(t) = 0

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(Sδ(d))d∈N is a sequence ofapproximate NPsif

limd→∞

Rδ(d)(t)

P= 0

• expected tracking rate

eδ(d)(t) = E

(

Rδ(d)(t)

)

(Sδ(d))d∈N has vanishing expected tracking rate, if

limd→∞

eδ(d)(t) = 0

=⇒

c© Copyright Eckhard Platen 10 BA - Toronto C 8 300

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limd→∞

P(

Rδ(d)(t) > ε

)

≤ limd→∞

1

εeδ(d)(t) = 0

Lemma 8.8 For a sequence of JDMs, any sequence of strictly positive

portfolios with vanishing expected tracking rate is a sequence of approximate

NPs.

c© Copyright Eckhard Platen 10 BA - Toronto C 8 301

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Diversification Theorem

Platen (2005a)

For a regular sequence of JDMs(SJD(d))d∈N , each sequence(Sδ

(d))d∈N

of DPs is a sequence of approximate NPs. Moreover

eδ(d)(t) ≤ (K2)

2K5

d2K1.

c© Copyright Eckhard Platen 10 BA - Toronto C 8 302

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Diversification in an MMM Setting

• savings account

S0(d)(t) = expr t

• discounted NP drift

αδ∗

t = α0 expη t

• jth benchmarked primary security account

Sj

(d)(t) =1

Y jt α

δ∗

t

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• SR process

dY jt =

(

1 − η Y jt

)

dt+

Y jt dW

jt

• NP

Sδ∗

(d)(t) =S0

(d)(t)

S0(d)(t)

• jth primary security account

Sj

(d)(t) = Sj

(d)(t)Sδ∗

(d)(t)

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0

50

100

150

200

250

300

350

400

450

0 5 9 14 18 23 27 32

Figure 8.1: Primary security accounts under the MMM.

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0

10

20

30

40

50

60

0 5 9 14 18 23 27 32

Figure 8.2: Benchmarked primary security accounts.

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0

10

20

30

40

50

60

70

80

90

100

0 5 9 14 18 23 27 32

EWI

GOP

Figure 8.3: NP and EWI.

c© Copyright Eckhard Platen 10 BA - Toronto C 8 307

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0

10

20

30

40

50

60

70

80

90

100

0 5 9 14 18 23 27 32

Market index

GOP

Figure 8.4: NP and market index.

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Real World Pricing for Two Market Models

Specifying a Continuous NP

market prices of event risks are zero

θkt = 0

NP

dSδ∗

t = Sδ∗

t

(

rt dt+

m∑

k=1

θkt

(

θkt dt+ dW k

t

)

)

Sδ∗

0 = 1

c© Copyright Eckhard Platen 10 BA - Toronto C 8 309

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Benchmarked Primary Security Accounts

dSjt = −Sj

t−

d∑

k=1

σj,kt dW k

t

Sjt = Sj

0 exp

−1

2

∫ t

0

m∑

k=1

(

σj,ks

)2ds−

m∑

k=1

∫ t

0

σj,ks dW k

s

× exp

∫ t

0

d∑

k=m+1

σj,ks

hk−ms ds

d∏

k=m+1

pk−mt∏

l=1

1 −σj,k

τkl −

hk−m

τkl −

pivotal objects of study

c© Copyright Eckhard Platen 10 BA - Toronto C 8 310

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• simplifying notation:

|σjt | =

m∑

k=1

(

σj,kt

)2

• aggregate continuous noise processes

W jt =

m∑

k=1

∫ t

0

σj,ks

|σjs|dW k

s

c© Copyright Eckhard Platen 10 BA - Toronto C 8 311

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• generalized volatility matrix bt = [bj,kt ]dj,k=1 invertible

bj,kt = θk

t − σj,kt

for k ∈ 1, 2, . . . ,m

bj,kt = −σj,k

t

k ∈ m+ 1, . . . , d

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• constant intensities

hkt = hk > 0

σj,kt = σj,k ≤

√hk−m

• benchmarkedjth primary security account:

Sjt = Sj,c

t Sj,dt

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• continuous part

Sj,ct = Sj

0 exp

−1

2

∫ t

0

|σjs|2 ds−

∫ t

0

|σjs| dW j

s

• compensated jump part

Sj,dt = exp

d∑

k=m+1

σj,k√hk−m t

d∏

k=m+1

(

1 − σj,k

√hk−m

)pk−mt

c© Copyright Eckhard Platen 10 BA - Toronto C 8 314

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Merton Model

rt = r, σj,kt = σj,k

Sj,ct = Sj

0 exp

−1

2|σj|2 t− |σj| W j

t

Girsanov’s theorem, see Section 9.5

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A Minimal Market Model with Jumps

Hulley, Miller & Pl. (2005)

• discounted NP drift

αj(t) = αj0 expηjt

ηj - net growth rate

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• jth square root process

dY jt =

(

1 − ηjY jt

)

dt+

Y jt dW

jt

• continuous part

Sj,ct =

1

αj(t)Y jt

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• time transformation

ϕj(t) = ϕj0 +

1

4

∫ t

0

αj(s) ds

• squared Bessel process of dimension four

Xj

ϕj(t)= αj(t)Y j

t =1

Sj,ct

S0 is a strict local martingale

c© Copyright Eckhard Platen 10 BA - Toronto C 8 318

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Zero Coupon Bonds

P (t, T ) = Sδ∗

t E

(

1

Sδ∗

T

At

)

=1

S0t

E

(

exp

−∫ T

t

rs ds

S0T

At

)

• MM case

P (t, T ) = exp−r(T−t) 1

S0t

E(

S0T

∣At

)

= exp−r(T−t)

c© Copyright Eckhard Platen 10 BA - Toronto C 8 319

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• MMM case

λjt =

1

Sjt (ϕ

j(t) − ϕj(T ))

S0T = S0,c

T

P (t, T ) = E

(

exp

−∫ T

t

rs ds

At

)

1

S0t

E(

S0T

∣At

)

= E

(

exp

−∫ T

t

rs ds

At

)

(

1 − exp

−1

2λ0

t

)

c© Copyright Eckhard Platen 10 BA - Toronto C 8 320

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Forward Contracts

Sδ∗

t E

(

F j(t, T ) − SjT

Sδ∗

T

At

)

= 0

forward price

F j(t, T ) =Sδ∗

t E(

SjT

∣At

)

Sδ∗

t E(

1

Sδ∗

T

∣At

) =

Sjt

P (t,T )1

Sjt

E(

SjT

∣At

)

if Sjt > 0

0 if Sjt = 0

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• MM caseF j(t, T ) = Sj

t expr(T − t)standard expression

• MMM case

1

Sjt

E(

SjT

∣At

)

=1

Sj,ct

E(

Sj,cT

∣At

) 1

Sj,dt

E(

Sj,dT

∣At

)

= 1 − exp

−1

2λj

t

forward price

F j(t, T ) = Sjt

1 − exp

−12λj

t

1 − exp−1

2λ0

t

(

E

(

exp

−∫ T

t

rs ds

At

))−1

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Asset-or-Nothing Binaries

Ingersoll (2000), Buchen (2004) and Buchen & Konstandatos (2005)

rt = r

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Aj,k(t, T,K) = Sδ∗

t E

(

1SjT ≥K

SjT

Sδ∗

T

At

)

=Sj

t

Sjt

E(

1SjT ≥K(S0

T )−1S0T S

jT

∣At

)

=Sj

t

Sj,ct

E

(

1Sj,cT ≥g(p

k−m

T −pk−mt )S0

T

× exp

σj,k√hk−m (T − t)

(

1 − σj,k

√hk−m

)pk−m

T −pk−mt

Sj,cT

At

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Aj,k(t, T,K) =

=

∞∑

n=0

exp−hk−m(T − t)

(hk(T − t))n

n!exp

σj,k√hk−m(T − t)

×(

1 − σj,k

√hk−m

)nSj

t

Sj,ct

E(

1Sj,cT ≥g(n)S0

T Sj,cT

∣At

)

for all t ∈ [0, T ], where

g(n) =K

S0t S

j,dt

exp

−(

r + σj,k√hk−m

)

(T − t)

(

1 − σj,k

√hk−m

)−n

for all n ∈ N

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MM case

Aj,k(t, T,K) =∞∑

n=0

exp−hk−m (T − t)

(hk−m (T − t))n

n!

× exp

σj,k√hk−m (T − t)

(

1 − σj,k

√hk−m

)n

Sjt N(d1(n))

for all t ∈ [0, T ], where

d1(n) =

ln(

Sjt

K

)

+

r + σj,k√hk−m + n

ln

(

1− σj,k√hk−m

)

T −t+ 1

2

(

σ0,j)2

(T − t)

σ0,j√T − t

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σi,j =√

|σi|2 − 2 i,j |σi| |σj| + |σj|2

i,j - correlation

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MMM case

S0 and Sj,c are independent

Aj,k(t, T,K) =

∞∑

n=0

exp−hk−m(T − t)

(hk−m(T − t))n

n!

× exp

σj,k√hk−m(T − t)

(

1 − σj,k

√hk−m

)n

×Sjt

(

G′′0,4

(ϕ0(T ) − ϕ0(t)

g(n);λj

t , λ0t

)

− exp

−1

2λj

t

)

c© Copyright Eckhard Platen 10 BA - Toronto C 8 328

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G′′0,4(x;λ, λ

′) equals probabilityP ( ZZ′

≤ x)

non-central chi-square distributed random variableZ ∼ χ2(0, λ)

non-central chi-square distributed random variableZ′ ∼ χ2(4, λ′)

c© Copyright Eckhard Platen 10 BA - Toronto C 8 329

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Bond-or-Nothing Binaries

MM case

Bj,k(t, T,K) =

∞∑

n=0

exp−hk−m (T − t)(hk−m (T − t))n

n!

×K exp−r(T − t)N(d2(n))

for all t ∈ [0, T ], where

d2(n) =

ln(

Sjt

K

)

+

(

r + σj,k√hk−m + n

ln(1− σj,k√hk−m

)

T −t− 1

2

(

σ0,j)2

)

(T − t)

σ0,j√T − t

= d1(n) − σ0,j√

T − t

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MMM case

Bj,k(t, T,K)

=

∞∑

n=0

exp−hk−m(T − t)(hk−m (T − t))n

n!

×K exp−r(T − t)(

1 −G′′0,4

(

(ϕj(T ) − ϕj(t))g(n);λ0t , λ

jt

))

c© Copyright Eckhard Platen 10 BA - Toronto C 8 331

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European Call Options

cj,kT,K(t) = Sδ∗

t E

(

SjT −K

)+

Sδ∗

T

At

= Sδ∗

t E

(

1SjT ≥K

SjT −K

Sδ∗

T

At

)

= Aj,k(t, T,K) −Bj,k(t, T,K)

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MM case

cj,kT,K(t) =

∞∑

n=0

exp−hk−m(T − t)(hk−m(T − t))n

n!

×(

exp

σj,k√hk−m (T − t)

(

1 − σj,k

√hk−m

)n

Sjt N(d1(n))

−K exp−r(T − t)N(d2(n))

)

c© Copyright Eckhard Platen 10 BA - Toronto C 8 333

Page 336: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

MMM case

cj,kT,K(t) =

∞∑

n=0

exp−hk−m(T − t)(hk−m(T − t))n

n!

×[

exp

σj,k√hk−m (T − t)

(

1 − σj,k

√hk−m

)n

×Sjt

(

G′′0,4

((

ϕ0(T ) − ϕ0(t)

g(n)

)

;λjt , λ

0t

)

− exp

−1

2λj

t

)

−K exp−r(T − t)(

1 −G′′0,4

(

(ϕj(T ) − ϕj(t))g(n);λ0t , λ

jt

))

]

c© Copyright Eckhard Platen 10 BA - Toronto C 8 334

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Defaultable Zero Coupon Bonds

maturityT

defaults at the first jump timeτk−m1 of pk−m

zero recovery

P k−m(t, T ) = Sδ∗

t E

(

1τk−m1 >T Sδ∗

T

At

)

= Sδ∗

t E

(

1

Sδ∗

T

At

)

E(

1τk−m1 >T

∣At

)

= P (t, T )P (pk−mT = 0

∣At)

c© Copyright Eckhard Platen 10 BA - Toronto C 8 335

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• conditional probability of survival

P(

pk−mT = 0

∣At

)

= E(

1pk−mt =0 1p

k−m

T −pk−mt =0

∣At

)

= 1pk−mt =0 P

(

pk−mT − pk−m

t = 0∣

∣At

)

= 1pk−mt =0E

(

exp

−∫ T

t

hk−ms ds

At

)

c© Copyright Eckhard Platen 10 BA - Toronto C 8 336

Page 339: A Benchmark Approach to Quantitative Finance · A Benchmark Approach to Quantitative Finance Eckhard Platen School of Finance and Economics and Department of Mathematical Sciences

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