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Advanced Microeconomic Theory
Chapter 7: Monopoly
Outline
β’ Barriers to Entryβ’ Profit Maximization under Monopolyβ’ Welfare Loss of Monopolyβ’ Multiplant Monopolistβ’ Price Discriminationβ’ Advertising in Monopolyβ’ Regulation of Natural Monopoliesβ’ Monopsony
Advanced Microeconomic Theory 2
Barriers to Entry
Advanced Microeconomic Theory 3
Barriers to Entry
β’ Entry barriers: elements that make the entry of potential competitors either impossible or very costly.
β’ Three main categories:1) Legal: the incumbent firm in an industry has the
legal right to charge monopoly prices during the life of the patent β Example: newly discovered drugs
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Barriers to Entry
2) Structural: the incumbent firm has a cost or demand advantage relative to potential entrants.β superior technologyβ a loyal group of customers positive network externalities (Facebook, eBay)
3) Strategic: the incumbent monopolist has a reputation of fighting off newcomers, ultimately driving them off the market.β price wars
Advanced Microeconomic Theory 5
Profit Maximization under Monopoly
Advanced Microeconomic Theory 6
Profit Maximization
β’ Consider a demand function π₯π₯(ππ), which is continuous and strictly decreasing in ππ, i.e., π₯π₯β² ππ < 0.
β’ We assume that there is price οΏ½Μ οΏ½π < β such that π₯π₯ ππ = 0 for all ππ > οΏ½Μ οΏ½π.
β’ Also, consider a general cost function ππ(ππ), which is increasing and convex in ππ.
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Profit Maximization
β’ οΏ½Μ οΏ½π is a βchoke priceβ
β’ No consumers buy positive amounts of the good for ππ > οΏ½Μ οΏ½π.
Advanced Microeconomic Theory 8
'( ) 0x p <
p
p
q
x(p)
( )=0 for all >x p p p
Profit Maximization
β’ Monopolistβs decision problem ismaxππ
πππ₯π₯ ππ β ππ(π₯π₯(ππ))
β’ Alternatively, using π₯π₯ ππ = ππ, and taking the inverse demand function ππ ππ = π₯π₯β1(ππ), we can rewrite the monopolistβs problem as
maxππβ₯0
ππ ππ ππ β ππ(ππ)
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Profit Maximization
β’ Differentiating with respect to ππ, ππ ππππ + ππβ² ππππ ππππ β ππβ² ππππ β€ 0
β’ Rearranging, ππ(ππππ) + ππβ² ππππ ππππ
ππππ=ππ ππ ππ ππππππ
β€ ππβ²(ππππ)ππππ
with equality if ππππ > 0.
β’ Recall that total revenue is πππ π ππ = ππ ππ ππ
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Profit Maximization
β’ In addition, we assume that ππ 0 β₯ ππβ²(0).β That is, the inverse demand curve originates
above the marginal cost curve.β Hence, the consumer with the highest willingness
to pay for the good is willing to pay more than the variable costs of producing the first unit.
β’ Then, we must be at an interior solution ππππ >0, implying
ππ(ππππ) + ππβ² ππππ ππππππππ
= ππβ²(ππππ)ππππ
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Profit Maximization
β’ Note that ππ ππππ + ππβ² ππππ ππππ
β= ππβ²(ππππ)
β’ Then, ππ ππππ > ππβ²(ππππ), i.e., monopoly price > ππππ
β’ Moreover, we know that in competitive equilibrium ππ ππβ = ππβ²(ππβ).
β’ Then, ππππ > ππβ and ππππ < ππβ.
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Profit Maximization
Advanced Microeconomic Theory 13
Profit Maximization
β’ Marginal revenue in monopoly πππ π = ππ ππππ + ππβ² ππππ ππππ
MR describes two effects:β A direct (positive) effect: an additional unit can be
sold at ππ ππππ , thus increasing revenue by ππ ππππ .β An indirect (negative) effect: selling an additional
unit can only be done by reducing the market price of all units (the new and all previous units), ultimately reducing revenue by ππβ² ππππ ππππ. Inframarginal units β initial units before the marginal
increase in output.Advanced Microeconomic Theory 14
Profit Maximization
β’ Is the above FOC also sufficient?β Letβs take the FOC ππ ππππ + ππβ² ππππ ππππ β ππβ² ππππ ,
and differentiate it wrt ππ,ππβ² ππ + ππβ² ππ + ππβ²β² ππ ππ
ππππππππππ
β ππβ²β²(ππ)ππππππππππ
β€ 0
β That is, ππππππππππ
β€ ππππππππππ
.
β Since MR curve is decreasing and MC curve is weakly increasing, the second-order condition is satisfied for all ππ.
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Profit Maximization
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p
q
x(p)
MC(q)
MR(q)
mp
mq
Profit Maximization
β’ What would happen if MC curve was decreasing in ππ (e.g., concave technology given the presence of increasing returns to scale)?β Then, the slopes of MR and MC curves are both
decreasing.β At the optimum, MR curve must be steeper MC
curve.
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Profit Maximization
Advanced Microeconomic Theory 18
p
q
x(p)MC(q)
MR(q)
mp
mq
Profit Maximization: Lerner Index
β’ Can we re-write the FOC in a more intuitive way? Yes.
β Just take πππ π = ππ ππ + ππβ² ππ ππ = ππ + ππππππππππ and
multiply by ππππ
,
πππ π = ππππππ
+οΏ½ππππππππ
ππππ
1/ππππ
ππ = ππ +1ππππππ
β In equilibrium, πππ π (ππ) = ππππ(ππ). Hence, we can replace MR with MC in the above expression.
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Profit Maximization: Lerner Index
β’ Rearranging yieldsππ βππππ(ππ)
ππ= β
1ππππ
β’ This is the Lerner index of market powerβ The price mark-up over marginal cost that a
monopolist can charge is a function of the elasticity of demand.
β’ Note:β If ππππ β β, then ππβππππ(ππ)
ππβ 0 βΉ ππ = ππππ(ππ)
β If ππππ β 0, then ππβππππ(ππ)ππ
β β βΉ substantial mark-upAdvanced Microeconomic Theory 20
Profit Maximization: Lerner Index
β’ The Lerner index can also be written as
ππ = ππππ(ππ)1+ 1
ππππ
which is referred to as the Inverse Elasticity Pricing Rule (IEPR).
β’ Example (Perloff, 2012): β Prilosec OTC: ππππ = β1.2. Then price should be ππ =
ππππ(ππ)1+ 1
β1.2= 6ππππ
β Designed jeans: ππππ = β2. Then price should be ππ =ππππ(ππ)1+ 1
β2= 2ππππ
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Profit Maximization: Lerner Index
β’ Example 1 (linear demand):β Market inverse demand function is
ππ ππ = ππ β ππππwhere ππ > 0
β Monopolistβs cost function is ππ ππ = ππππβ We usually assume that ππ > ππ β₯ 0 To guarantee ππ 0 > ππβ²(0) That is, ππ 0 = ππ β πππ = ππ and ππβ² ππ = ππ, thus
implying ππβ² 0 = ππ
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Profit Maximization: Lerner Index
β’ Example 1 (continued):β Monopolistβs objective function
ππ ππ = ππ β ππππ ππ β ππππ
β FOC: ππ β 2ππππ β ππ = 0β SOC: β2ππ < 0 (concave) Note that as long as ππ > 0, i.e., negatively sloped
demand function, profits will be concave in output. Otherwise (i.e., Giffen good, with positively sloped
demand function) profits will be convex in output.
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Profit Maximization: Lerner Index
β’ Example 1 (continued):β Solving for the optimal ππππ in the FOC, we find
monopoly output
ππππ =ππ β ππ2ππ
β Inserting ππππ = ππβππ2ππ
in the demand function, we obtain monopoly price
ππππ = ππ β ππππ β ππ2ππ
=ππ + ππ
2β Hence, monopoly profits are
ππππ = ππππππππ β ππππππ =ππ β ππ 2
4ππAdvanced Microeconomic Theory 24
Profit Maximization: Lerner Index
β’ Example 1 (continued):
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Profit Maximization: Lerner Index
β’ Example 1 (continued):
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p
12
abβ
mq ab
cβ(q)
q
mp
a
MR=a-2bqp(q)=a-bq
β Non-constant marginal cost
β The cost function is convex in outputππ(ππ) = ππππ2
β Marginal cost isππβ²(ππ) = 2ππππ
Profit Maximization: Lerner Index
β’ Example 2 (Constant elasticity demand):β The demand function is
ππ(ππ) = π΄π΄ππβππ
β We can show that ππ ππ = βππ for all ππ, i.e.,
ππ ππ =ππππ(ππ)ππππ
ππππ
= βππ π΄π΄ππβππβ1ππππ(ππ)ππππ
πππ΄π΄ππβππππππ
= βππππβππ
ππππππβππ
= βππ
Advanced Microeconomic Theory 27
Profit Maximization: Lerner Index
β’ Example 2 (continued):β We can now plug ππ ππ = βππ into the Lerner
index,
ππππ =ππ
1 + 1ππ ππ
=ππ
1 β 1ππ
=ππππ
ππ β 1
β That is, price is a constant mark-up over marginal cost.
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Welfare Loss of Monopoly
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p
q
p(q)
cβ(q)
MR=p(q)+pβ(q)q
mp
mq
*p
*q
( )mp qA
B CED
[ ]*
( ) '( )m
q
qp s c s dsββ«
Welfare Loss of Monopoly
β’ Welfare comparison for perfect competition and monopoly.
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Welfare Loss of Monopoly
β’ Consumer surplusβ Perfect competition: A+B+Cβ Monopoly: A
β’ Producer surplus:β Perfect competition: D+Eβ Monopoly: B+D
β’ Deadweight loss of monopoly: C+E
π·π·π·π·π·π· = οΏ½ππππ
ππβ
ππ π π β ππβ²(π π ) πππ π
β’ DWL decreases as demand and/or supply become more elastic.
Advanced Microeconomic Theory 31
p
p
mq
*q
cβ(q)
q
Coincides with (PC market)
( )p q p=
Welfare Loss of Monopolyβ’ Infinitely elastic demand
ππβ² ππ = 0β’ The inverse demand curve
becomes totally flat.β’ Marginal revenue coincides
with inverse demand:πππ π ππ = ππ ππ + 0 οΏ½ ππ= ππ(ππ)
β’ Profit-maximizing πππππ π ππ = ππππ ππ βΉππ ππ = ππππ(ππ)
β’ Hence, ππππ = ππβ and π·π·π·π·π·π· = 0.
Advanced Microeconomic Theory 32
Welfare Loss of Monopoly
β’ Example (Welfare losses and elasticity):β Consider a monopolist with constant marginal and
average costs, ππβ² ππ = ππ, who faces a market demand with constant elasticity
ππ ππ = ππππ
where ππ is the price elasticity of demand (ππ < β1)β Perfect competition: ππππ = ππβ Monopoly: using the IEPR
ππππ =ππ
1 + 1ππ
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Welfare Loss of Monopolyβ’ Example (continued):
β The consumer surplus associated with any price (ππ0) can be computed as
πππΆπΆ = οΏ½ππ0
βππ ππ ππππ = οΏ½
ππ0
βππππππππ = οΏ½
ππππ+1
ππ + 1ππ0
β
= βππ0ππ+1
ππ + 1<0
> 0
β Under perfect competition, ππππ = ππ,
πππΆπΆ = βππππ+1
ππ + 1β Under monopoly, ππππ = ππ
1+1/ππ,
πππΆπΆππ = β
ππ1 + 1/ππ
ππ+1
ππ + 1
Advanced Microeconomic Theory 34
Welfare Loss of Monopoly
β’ Example (continued):β Taking the ratio of these two surpluses
πππΆπΆπππππΆπΆ
=1
1 + 1/ππ
ππ+1
β If ππ = β2, this ratio is Β½ CS under monopoly is half of that under perfectly
competitive markets
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Welfare Loss of Monopoly
β’ Example (continued):
β The ratio πππΆπΆπππππΆπΆ
= 11+1/ππ
ππ+1decreases as demand becomes
more elastic (ππ increases in absolute value).
Advanced Microeconomic Theory 36
Welfare Loss of Monopoly
β’ Example (continued):β Monopoly profits are given by
ππππ = ππππππππ β ππππππ =ππ
1 + 1/ππβ ππ ππππ
where ππππ(ππ) = ππππ = ππ1+1/ππ
ππ.
β Rearranging,
ππππ =βππ/ππ
1 + 1/ππππ
1 + 1/ππ
ππ
= βππ
1 + 1/ππ
ππ+1
οΏ½1ππ
Advanced Microeconomic Theory 37
Welfare Loss of Monopoly
β’ Example (continued):β To find the transfer from CS into monopoly profits
that consumers experience when moving from perfect competition to a monopoly, divide monopoly profits by the competitive CS
ππππ
πππΆπΆ= ππ+1
ππ1
1+1/ππ
ππ+1= ππ
1+ππ
ππ
β If ππ = β2, this ratio is ΒΌ One-fourth of the consumer surplus under perfectly
competitive markets is transferred to monopoly profitsAdvanced Microeconomic Theory 38
Welfare Loss of Monopoly
β’ More social costs of monopoly:β Excessive R&D expenditure (patent race)β Persuasive (not informative) advertisingβ Lobbying costs (different from bribes)β Resources to avoid entry of potential firms in the
industry
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Comparative Statics
Advanced Microeconomic Theory 40
p
p(q)MR
2mq
1mp
1mq
'2 ( )c q
'1( )c q
2mp
Comparative Statics
β’ We want to understand how ππππ varies as a function of the monopolistβs marginal cost
Advanced Microeconomic Theory 41
Comparative Staticsβ’ Formally, we know that at the optimum, ππππ(ππ), the
monopolist maximizes its profitsππππ ππππ ππ , ππ
ππππππ= 0
β’ Differentiating wrt ππ, and using the chain rule,ππ2ππ ππππ ππ , ππ
ππππ2ππππππ ππππππ
+ππ2ππ ππππ ππ , ππ
ππππππππ= 0
β’ Solving for ππππππ ππππππ
, we have
ππππππ ππππππ
= β
ππ2ππ ππππ ππ , ππππππππππ
ππ2ππ ππππ ππ , ππππππ2
Advanced Microeconomic Theory 42
Comparative Statics
β’ Example:β Assume linear demand curve ππ ππ = ππ β ππππβ Then, the cross-derivative is
ππ2ππ ππππ ππ , ππππππππππ
=ππ ππ ππ β ππππ ππ β ππππ
ππππππππ
=ππ ππ β 2ππππ β ππ
ππππ= β1
and
ππππππ ππππππ
= β
ππ2ππ ππππ ππ , ππππππππππ
ππ2ππ ππππ ππ , ππππππ2
= ββ1β2ππ
< 0
Advanced Microeconomic Theory 43
Comparative Statics
β’ Example (continued):β That is, an increase in marginal cost, ππ, decreases
monopoly output, ππππ.β Similarly for any other demand. β Even if we donβt know the accurate demand
function, but know the sign of
ππ2ππ ππππ ππ , ππππππππππ
Advanced Microeconomic Theory 44
Comparative Statics
β’ Example (continued):
Advanced Microeconomic Theory 45
β Marginal costs are increasing in ππ
β For convex cost curve ππ ππ = ππππ2, monopoly output isππππ ππ =
ππ2(ππ + ππ)
β Here, ππππππ ππππππ
= βππ
2 ππ + ππ 2 < 0
Comparative Statics
β’ Example (continued):
Advanced Microeconomic Theory 46
β Constant marginal costβ For the constant-elasticity
demand curve ππ ππ = ππππ, we have ππππ = ππ
1+1/ππand
ππππ(ππ) = ππππ1+ππ
ππ
β Here,ππππππ ππππππ
=ππππ
ππππ1 + ππ
ππ
=ππππππππ < 0
Multiplant Monopolist
Advanced Microeconomic Theory 47
Multiplant Monopolist
β’ Monopolist produces output ππ1, ππ2, β¦ , ππππ across ππ plants it operates, with total costs ππππππ(ππππ) at each plant ππ = {1,2, β¦ ,ππ}.
β’ Profits-maximization problemmaxππ1,β¦,ππππ
ππ β ππβππ=1ππ ππππ βππ=1ππ ππππ β βππ=1ππ ππππππ(ππππ)
β’ FOCs wrt production level at every plant ππ
ππ β 2πποΏ½ππ=1
ππππππ β ππππππ ππππ = 0
βΊπππ π ππ = ππππππ(ππππ)for all ππ.
Advanced Microeconomic Theory 48
Multiplant Monopolist
β’ Multiplant monopolist operating two plants with marginal costs ππππ1 and ππππ2.
Advanced Microeconomic Theory 49
Multiplant Monopolist
β’ Total marginal cost is πππππ‘π‘π‘π‘π‘π‘πππ‘π‘ = ππππ1 + ππππ2 (i.e., horizontal sum)
β’ πππ‘π‘π‘π‘π‘π‘πππ‘π‘ is determined by πππ π = πππππ‘π‘π‘π‘π‘π‘πππ‘π‘ (i.e., point A)
β’ Mapping πππ‘π‘π‘π‘π‘π‘πππ‘π‘ in the demand curve, we obtain price ππππ (both plants selling at the same price)
β’ At the MC level for which πππ π = πππππ‘π‘π‘π‘π‘π‘πππ‘π‘ (i.e., point A), extend a line to the left crossing ππππ1and ππππ2.
β’ This will give us output levels ππ1 and ππ2 that plants 1 and 2 produce, respectively.
Advanced Microeconomic Theory 50
Multiplant Monopolist
β’ Example 1 (symmetric plants):β Consider a monopolist operating ππ plants, where
all plants have the same cost function ππππππ ππππ =πΉπΉ + ππππππ2. Hence, all plants produce the same output level ππ1 = ππ2 = β― = ππππ = ππ and ππ = ππππππ. The linear demand function is given by ππ = ππ β ππππ.
β FOCs:ππ β 2ππβππ=1ππ ππππ = 2ππππππ or ππ β 2ππππππππ = 2ππππππ
ππππ =ππ
2(ππππ + ππ)Advanced Microeconomic Theory 51
Multiplant Monopolistβ’ Example 1 (continued):
β Total output produced by the monopolist is
ππ = ππππππ=ππππ
2(ππππ + ππ)and market price is
ππ = ππ β ππππ = ππ β ππππππ
2 ππππ + ππ=ππ(ππππ + 2ππ)2 ππππ + ππ
β Hence, the profits of every plant ππ are
ππππ =ππ(ππππ + 2ππ)2 ππππ + ππ
ππ2(ππππ + ππ)
β ππππ
2(ππππ + ππ)
2
=ππ2
4 ππππ + ππβ πΉπΉ
β Total profits become
πππ‘π‘π‘π‘π‘π‘πππ‘π‘ =ππππ2
4 ππππ + ππβ πππΉπΉ
Advanced Microeconomic Theory 52
Multiplant Monopolist
β’ Example 1 (continued):β The optimal number of plants ππβ is determined by
πππππ‘π‘π‘π‘π‘π‘πππ‘π‘ππππ
=ππ2
4ππ
(ππππ + ππ)2β πΉπΉ = 0
and solving for ππ
ππβ =1ππ
ππ2
πππΉπΉβ ππ
β ππβ is decreasing in the fixed costs πΉπΉβ ππβ is decreasing in ππ as long as ππ < 4 πππΉπΉ, since
ππππβ
ππππ=
1ππ
ππ β 4 πππΉπΉ4 πππΉπΉ
Advanced Microeconomic Theory 53
Multiplant Monopolist
β’ Example 1 (continued):β Note that when ππ = 1, ππ = ππππ and ππ = ππππ.β Note that an increase in ππ decreases ππππ and ππππ, as
ππππππππππ
= βππππ
2 ππππ + ππ 2 < 0
ππππππππππ
= βππ2ππ
4 ππππ + ππ 2 < 0
Advanced Microeconomic Theory 54
Multiplant Monopolist
β’ Example 2 (asymmetric plants):β Consider a monopolist operating two plants with
marginal costs ππππ1 ππ1 = 10 + 20ππ1 and ππππ2 ππ2 =60 + 5ππ2, respectively. A linear demand function is give by ππ ππ = 120 β 3ππ.
β Note that πππππ‘π‘π‘π‘π‘π‘πππ‘π‘ β ππππ1(ππ1) + ππππ2(ππ2) This is a vertical (not a horizontal) sum.
β Instead, first invert the marginal cost functions
ππππ1 ππ1 = 10 + 20ππ1 βΊ ππ1 =ππππ120
β12
ππππ2 ππ2 = 60 + 5ππ2 βΊ ππ2 =ππππ2
5β 12
Advanced Microeconomic Theory 55
Multiplant Monopolist
β’ Example 2 (continued):β Second,
πππ‘π‘π‘π‘π‘π‘πππ‘π‘ = ππ1 + ππ2 =πππππ‘π‘π‘π‘π‘π‘πππ‘π‘
20β
12
+πππππ‘π‘π‘π‘π‘π‘πππ‘π‘
5β 12
=14πππππ‘π‘π‘π‘π‘π‘πππ‘π‘ β 12.5
β Hence, πππππ‘π‘π‘π‘π‘π‘πππ‘π‘ = 50 + 4πππ‘π‘π‘π‘π‘π‘πππ‘π‘β Setting πππ π ππ = 120 β 6ππ = 50 + 4ππ = πππππ‘π‘π‘π‘π‘π‘πππ‘π‘, we
obtain πππ‘π‘π‘π‘π‘π‘πππ‘π‘ = 7 and ππ = 120 β 3 οΏ½ 7 = 99.β Since πππ π πππ‘π‘π‘π‘π‘π‘πππ‘π‘ = 120 β 6 οΏ½ 7 = 78, then πππ π πππ‘π‘π‘π‘π‘π‘πππ‘π‘ = ππππ1 ππ1 βΉ 78 = 10 + 20ππ1 βΉ ππ1 = 3.4πππ π πππ‘π‘π‘π‘π‘π‘πππ‘π‘ = ππππ2 ππ2 βΉ 78 = 60 + 5ππ2 βΉ ππ2 = 3.6
Advanced Microeconomic Theory 56
Price Discrimination
Advanced Microeconomic Theory 57
p
q
MR p(q)
mp MC
*qmqSelling these units at mp p>
Selling these units at mp p<
Price Discrimination
β’ Can the monopolist capture an even larger surplus?
Advanced Microeconomic Theory 58
β Charge ππ > ππππ to those who buy the product at ππππand are willing to pay more
β Charge ππ < ππ < ππππ to those who do not buy the product at ππππ, but whose willingness to pay for the good is still higher than the marginal cost of production, ππ.
β With ππππ for all units, the monopolist does not capture the surplus of neither of these segments.
Price
Quantity
D
2q1...q
Price Discrimination: First-degree
β’ First-degree (perfect) price discrimination:β The monopolist charges to every customer his/her
maximum willingness to pay for the object.
Advanced Microeconomic Theory 59
β Personalized price: The first buyer pays ππ1 for the ππ1 units, the second buyer pays ππ2 for ππ2 β ππ1units, etc.
Price Discrimination: First-degree
β The monopolist continues doing so until the last buyer is willing to pay the marginal cost of production.
β In the limit, the monopolist captures all the area below the demand curve and above the marginal cost (i.e., consumer surplus).
Advanced Microeconomic Theory 60
p
q
p(q)
' ( )c q
*q
MR
Profits
mq
Price Discrimination: First-degree
β’ Suppose that the monopolist can charge a fixed fee, ππβ, and an amount of the good, ππβ, that maximizes profits.
β’ PMP:maxππ,ππ
ππ β ππππ
π π . π‘π‘. π’π’(ππ) β₯ ππβ’ Note that the monopolist raises the fee ππ until π’π’ ππ = ππ.
Hence we can reduce the set of choice variablesmaxππ
π’π’(ππ) β ππππ
β’ FOC: π’π’β² ππβ β ππ = 0 or π’π’β² ππβ = ππ. β Intuition: the monopolist increases output until the
marginal utility that consumers obtain from additional units coincides with the marginal cost of production
Advanced Microeconomic Theory 61
Price Discrimination: First-degree
β’ Given the level of production ππβ, the optimal fee is
ππβ = π’π’ ππβ
β’ Intuition: the monopolist charges a fee ππβ that coincides with the utility that the consumer obtains from consuming ππβ.
Advanced Microeconomic Theory 62
p
q
p(q)
' ( )c q
*CEq q=
MR
mq
**
0Profits ( ) ( )
qp q dq c q= ββ«
*r
mp
Price Discrimination: First-degree
β’ Example:β A monopolist faces inverse demand curve ππ ππ =
20 β ππ and constant marginal costs ππ = $2. β No price discrimination:
πππ π = ππππ βΉ 20 β 2ππ = 2 βΉ ππππ = 9ππππ = $11, ππππ = $81
β Price discrimination:ππ ππ = ππππ βΉ 20 β ππ = 2 βΉππ = 18
ππ =18 Γ 20 β 2
2= $162
Advanced Microeconomic Theory 63
Price Discrimination: First-degree
β’ Example (continued):
Advanced Microeconomic Theory 64
Price Discrimination: First-degree
β’ Summary:β Total output coincides with that in perfect
competitionβ Unlike in perfect competition, the consumer does
not capture any surplusβ The producer captures all the surplusβ Due to information requirements, we do not see
many examples of it in real applications Financial aid in undergraduate education (βtuition
discriminationβ)Advanced Microeconomic Theory 65
Price Discrimination: First-degree
β’ Example (two-block pricing):
Advanced Microeconomic Theory 66
β A monopolist faces a inverse demand curve ππ ππ = ππ β ππππ , with constant marginal costs ππ < ππ.
β Under two-block pricing, the monopolist sells the first ππ1 units at a price ππ(ππ1) = ππ1 and the remaining ππ2 β ππ1units at a price ππ(ππ2) = ππ2.
Price Discrimination: First-degree
β’ Example (continued):β Profits from the first ππ1 units
ππ1 = ππ ππ1 οΏ½ ππ1 β ππππ1 = (ππ β ππππ1 β ππ)ππ1while from the remaining ππ2 β ππ1 units
ππ2 = ππ ππ2 οΏ½ ππ2 β ππ1 β ππ οΏ½ (ππ2 βππ1)= (ππ β ππππ2 β ππ)(ππ2βππ1)
β Hence total profits areππ = ππ1 + ππ2= ππ β ππππ1 β ππ ππ1 + (ππ β ππππ2 β ππ)(ππ2βππ1)
Advanced Microeconomic Theory 67
Price Discrimination: First-degreeβ’ Example (continued):
β FOCs:ππππππππ1
= ππ β 2ππππ1 β ππ β ππ + ππππ2 + ππ = 0
ππππππππ2
= βππ ππ2 β ππ1 + ππ β ππππ2 β ππ = 0
β Solving for ππ1 and ππ2ππ1 =
ππ β ππ3ππ
ππ2 =2(ππ β ππ)
3ππwhich entails prices of
ππ ππ1 = ππ β ππ οΏ½ππ β ππ3ππ
=2ππ + ππ
3ππ ππ2 =
ππ + 2ππ3
where ππ ππ1 > ππ ππ2 since ππ > ππ.Advanced Microeconomic Theory 68
Price Discrimination: First-degree
β’ Example (continued):β The monopolistβs profits from each block are
ππ1 = ππ ππ1 β ππ οΏ½ ππ1
=2ππ + ππ
3β ππ οΏ½
ππ β ππ3ππ
=2ππππ β ππ
3
2
ππ2 = ππ ππ2 β ππ)(ππ2 β ππ1
=ππ + 2ππ
3β ππ οΏ½
2 ππ β ππ3ππ
βππ β ππ3ππ
=1ππππ β ππ
3
2
β Thus, ππ = ππ1 + ππ2 = ππβππ 2
3ππ, which is larger than
those arising from uniform pricing , πππ’π’ = ππβππ 2
4ππ.
Advanced Microeconomic Theory 69
Price Discrimination: Third-degree β’ Third degree price discrimination:
β The monopolist charges different prices to two or more groups of customers (each group must be easily recognized by the seller).
β’ Example: youth vs. adult at the movies, airline tickets β Firmβs PMP:
maxπ₯π₯1,π₯π₯2
ππ1 π₯π₯1 π₯π₯1 + ππ2 π₯π₯2 π₯π₯2 β πππ₯π₯1 β πππ₯π₯2β FOCs:
ππ1 π₯π₯1 + ππ1β² π₯π₯1 π₯π₯1 β ππ = 0 βΉ πππ π 1 = ππππππ2 π₯π₯2 + ππ2β² π₯π₯2 π₯π₯2 β ππ = 0 βΉ πππ π 2 = ππππ
β FOCs coincides with those of a regular monopolist who serves two completely separated markets practicing uniform pricing .
Advanced Microeconomic Theory 70
1p
1MR
1 14x =
$10$10MC =
1 $24p =
1x
2p
2 8x =2MR
2 $12p =
2x
Market 1Adults at the movies
Market 2Seniors at the movies
1( )p x 2( )p x
Price Discrimination: Third-degreeβ Example: ππ1 π₯π₯1 = 38 β π₯π₯1 for adults and ππ2 π₯π₯2 = 14 β
1/4π₯π₯2 for seniors, with ππππ = $10 for both markets.πππ π 1 π₯π₯1 = ππππ βΉ 38 β 2π₯π₯1 = 10 βΉ π₯π₯1 = 14 ππ1 = $24πππ π 2 π₯π₯2 = ππππ βΉ 14 β 1/2π₯π₯2 = 10 βΉ π₯π₯2 = 8 ππ2 = $12
Advanced Microeconomic Theory 71
Price Discrimination: Third-degree
β’ Using the Inverse Elasticity Pricing Rule (IERP), we can obtain the prices
ππ1 π₯π₯1 = ππ1β1/ππ1
and ππ2 π₯π₯2 = ππ1β1/ππ2
where ππ is the common marginal costβ’ Then, ππ1 π₯π₯1 > ππ2 π₯π₯2 if and only if
ππ1β1/ππ1
> ππ1β1/ππ2
βΉ 1 β 1ππ2
< 1 β 1ππ1
βΉ1ππ2
>1ππ1βΉ ππ2 < ππ1
β’ Intuition: the monopolist charges lower price in the market with more elastic demand.
Advanced Microeconomic Theory 72
Price Discrimination: Third-degree
β’ Example (Pullman-Seattle route):β The price-elasticity of demand for business-class
seats is -1.15, while that for economy seats is -1.52β From the IEPR,
πππ΅π΅ =ππππ
1 β 1/1.15βΉ 0.13πππ΅π΅ = ππππ
πππΈπΈ =ππππ
1 β 1/1.52βΉ 0.34πππΈπΈ = ππππ
β Hence, 0.13πππ΅π΅ = 0.34πππΈπΈ or πππ΅π΅ = 2.62πππΈπΈ Airline maximizes its profits by charging business-class
seats a price 2.62 times higher than that of economy-class seats
Advanced Microeconomic Theory 73
Price Discrimination: Second-degree
β’ Second-degree price discrimination:β The monopolist cannot observe the type of each
consumer (e.g., his willingness to pay).β Hence the monopolist offers a menu of two-part
tariffs, (πΉπΉπΏπΏ, πππΏπΏ) and (πΉπΉπ»π», πππ»π»), with the property that the consumer with type ππ = {π·π·,π»π»} has the incentive to self-select the two-part tariff (πΉπΉππ , ππππ)meant for him.
Advanced Microeconomic Theory 74
Price Discrimination: Second-degree
β’ Assume the utility function of type ππ consumerππππ ππππ ,πΉπΉππ = πππππ’π’ ππππ β πΉπΉππ
where β ππππ is the quantity of a good consumedβ πΉπΉππ is the fixed fee paid to the monopolist for ππππβ ππππ measures the valuation consumer assigns to the
good, where πππ»π» > πππΏπΏ, with corresponding probabilities ππ and 1 β ππ.
β’ The monopolistβs constant marginal cost ππsatisfies ππππ > ππ for all ππ = {π·π·,π»π»}.
Advanced Microeconomic Theory 75
Price Discrimination: Second-degree
β’ The monopolist must guarantee that1) both types of customers are willing to
participate (βparticipation constraintβ) the two-part tariff meant for each type of customer
provides him with a weakly positive utility level
2) customers do not have incentives to choose the two-part tariff meant for the other type of customer (βincentive compatibilityβ) type ππ customer prefers (πΉπΉππ , ππππ) over (πΉπΉππ , ππππ) where ππ β ππ
Advanced Microeconomic Theory 76
Price Discrimination: Second-degree
β’ The participation constraints (PC) areπππΏπΏπ’π’(πππΏπΏ) β πΉπΉπΏπΏ β₯ 0 πππππΏπΏπππ»π»π’π’(πππ»π») β πΉπΉπ»π» β₯ 0 πππππ»π»
β’ The incentive compatibility conditions areπππΏπΏπ’π’(πππΏπΏ) β πΉπΉπΏπΏ β₯ πππΏπΏπ’π’(πππ»π») β πΉπΉπ»π» πΌπΌπππΏπΏπππ»π»π’π’(πππ»π») β πΉπΉπ»π» β₯ πππ»π»π’π’(πππΏπΏ) β πΉπΉπΏπΏ πΌπΌπππ»π»
Advanced Microeconomic Theory 77
Price Discrimination: Second-degree
β’ Rearranging the four inequalities, the monopolistβs profit maximization problem becomes:
maxπΉπΉπΏπΏ,πππΏπΏ,πΉπΉπ»π»,πππ»π»
ππ πΉπΉπ»π» β πππππ»π» + 1 β ππ [πΉπΉπΏπΏ β πππππΏπΏ]
πππΏπΏπ’π’(πππΏπΏ) β₯ πΉπΉπΏπΏπππ»π»π’π’(πππ»π») β₯ πΉπΉπ»π»
πππΏπΏ π’π’(πππΏπΏ) β π’π’(πππ»π») + πΉπΉπ»π» β₯ πΉπΉπΏπΏπππ»π» π’π’(πππ»π») β π’π’(πππΏπΏ) + πΉπΉπΏπΏ β₯ πΉπΉπ»π»
Advanced Microeconomic Theory 78
Price Discrimination: Second-degree
β’ Both πππππ»π» and πΌπΌπππ»π» are expressed in terms of the fee πΉπΉπ»π»β The monopolist increases πΉπΉπ»π» until such fee coincides
with the lowest of πππ»π»π’π’(πππ»π») and πππ»π»[]
π’π’(πππ»π») βπ’π’(πππΏπΏ) + πΉπΉπΏπΏ for all ππ = {π·π·,π»π»}
β Otherwise, one (or both) constraints will be violated, leading the high-demand customer to not participate
Advanced Microeconomic Theory 79
Price Discrimination: Second-degree
Advanced Microeconomic Theory 80
Price Discrimination: Second-degree
β’ High-demand customer:β Let us show that πΌπΌπππ»π» is binding
β An indirect way to show that
πΉπΉπ»π» = πππ»π» π’π’(πππ»π») β π’π’(πππΏπΏ) + πΉπΉπΏπΏ
is to demonstrate that πΉπΉπ»π» < πππ»π»π’π’(πππ»π»)
β Proving this by contradiction, assume that πΉπΉπ»π» = πππ»π»π’π’(πππ»π»)
Advanced Microeconomic Theory 81
Price Discrimination: Second-degreeβ Then, πΌπΌπππ»π» can be written as
πΉπΉπ»π» β πππ»π»π’π’ πππΏπΏ + πΉπΉπΏπΏ β₯ πΉπΉπ»π»βΉ πΉπΉπΏπΏ β₯ πππ»π»π’π’(πππΏπΏ)
β Combining this result with the fact that πππ»π» > πππΏπΏ,πΉπΉπΏπΏ β₯ πππ»π»π’π’ πππΏπΏ > πππΏπΏπ’π’ πππΏπΏ
which implies πΉπΉπΏπΏ > πππΏπΏπ’π’ πππΏπΏ
β However, this violates πππππΏπΏ We then reached a contradiction Thus, πΉπΉπ»π» < πππ»π»π’π’(πππ»π») πΌπΌπππ»π» is binding but πππππ»π» is not.
Advanced Microeconomic Theory 82
Price Discrimination: Second-degree
β’ Low-demand customer:β Let us show that πππππΏπΏ binding
β Similarly as for the high-demand customer, an indirect way to show that
πΉπΉπΏπΏ = πππΏπΏπ’π’(πππΏπΏ)is to demonstrate that πΉπΉπΏπΏ < πππΏπΏ π’π’(πππΏπΏ) β π’π’(πππ»π») + πΉπΉπ»π»
β Proving this by contradiction, assume that πΉπΉπΏπΏ = πππΏπΏ π’π’ πππΏπΏ β π’π’ πππ»π» + πΉπΉπ»π»
Advanced Microeconomic Theory 83
Price Discrimination: Second-degree
β Then, πΌπΌπππ»π» can be written as
πππ»π» π’π’(πππ»π») β π’π’(πππΏπΏ) + πππΏπΏ π’π’(πππΏπΏ) β π’π’(πππ»π») + πΉπΉπ»π» = πΉπΉπ»π»βΉ πππ»π» π’π’(πππ»π») β π’π’(πππΏπΏ) = πππΏπΏ π’π’(πππ»π») β π’π’(πππΏπΏ)βΉ πππ»π» = πππΏπΏ
which violates the initial assumption πππ»π» > πππΏπΏ We reached a contradiction Thus, πΉπΉπΏπΏ < πππΏπΏ π’π’ πππΏπΏ β π’π’ πππ»π» + πΉπΉπ»π» πππππΏπΏ is binding but πΌπΌπππΏπΏ is not
Advanced Microeconomic Theory 84
Price Discrimination: Second-degree
β’ In summary:β From πππππΏπΏ binding we have
πππΏπΏπ’π’ πππΏπΏ = πΉπΉπΏπΏβ From πΌπΌπππ»π» binding we have
πππ»π» π’π’ πππ»π» β π’π’ πππΏπΏ + πΉπΉπΏπΏ = πΉπΉπ»π»β In addition,
β’ πππππΏπΏ binding implies that πΌπΌπππΏπΏ holds, and β’ πΌπΌπππ»π» binding entails that πππππ»π» is also satisfied, β’ That is, all four constraints hold.
Advanced Microeconomic Theory 85
Price Discrimination: Second-degree
β’ The monopolistβs expected PMP can then be written as unconstrained problem, as follows,
maxπππΏπΏ,πππ»π»β₯0
ππ πΉπΉπ»π» β πππππ»π» + 1 β ππ [πΉπΉπΏπΏ β πππππΏπΏ]
= ππ πππ»π» π’π’ πππ»π» β π’π’ πππΏπΏ + πΉπΉπΏπΏπΉπΉπ»π»
β πππππ»π»
+ 1 β ππ πππΏπΏπ’π’ πππΏπΏπΉπΉπΏπΏ
β πππππΏπΏ
= ππ πππ»π» π’π’ πππ»π» β π’π’ πππΏπΏ + πππΏπΏπ’π’ πππΏπΏπΉπΉπΏπΏ
β πππππ»π»
+ 1 β ππ πππΏπΏπ’π’ πππΏπΏ β πππππΏπΏ= ππ πππ»π»π’π’ πππ»π» β πππ»π» β πππΏπΏ π’π’ πππΏπΏ β πππππ»π»
+(1 β ππ) πππΏπΏπ’π’ πππΏπΏ β πππππΏπΏ
Advanced Microeconomic Theory 86
Price Discrimination: Second-degree
β’ FOC with respect to πππ»π»:ππ πππ»π»π’π’β²(πππ»π») β ππ = 0 βΉ πππ»π»π’π’β²(πππ»π») = ππ
β which coincides with that under complete information. β That is, there is not output distortion for high-demand buyer β Informally, we say that there is βno distortion at the topβ.
β’ FOC with respect to πππΏπΏ:ππ β(πππ»π» β πππΏπΏ)π’π’β²(πππΏπΏ) + 1 β ππ πππΏπΏπ’π’β²(πππΏπΏ) β ππ = 0
which can be re-written as
π’π’β²(πππΏπΏ) πππΏπΏ β πππππ»π» = 1 β ππ ππAdvanced Microeconomic Theory 87
Price Discrimination: Second-degree
β’ Dividing both sides by 1 β ππ , we obtain
π’π’β²(πππΏπΏ) πππΏπΏβπππππ»π»1βππ
= ππ
β’ The above expression can alternatively be written as
π’π’β²(πππΏπΏ) πππΏπΏ βππ
1βπππππ»π» β πππΏπΏ = ππ
Advanced Microeconomic Theory 88
Price Discrimination: Second-degree
β’ The output offered to low-demand customers entails a distortion, i.e., πππΏπΏ < πππΏπΏπ π π‘π‘
β’ Per-unit price for high-type and low-type differs, i.e., πΉπΉπ»π» β πΉπΉπΏπΏβ Monopolist practices price
discrimination among the two types of customers.
Advanced Microeconomic Theory 89
β’ π’π’β²(πππΏπΏ) οΏ½ πππΏπΏ depicts the socially optimal output πππΏπΏπ π π‘π‘, i.e., that arising under complete information
β’ The output offered to high-demand customers is socially efficient due to the absence of output distortion for high-type agents
Price Discrimination: Second-degree
β’ Since constraint πππππΏπΏ binds while πππππ»π» does not, then only the high-demand customer retains a positive utility level, i.e., πππ»π»π’π’(πππ»π») β πΉπΉπ»π» > 0.
β’ The firmβs lack of information provides the high-demand customer with an βinformation rent.β β Intuitively, the information rent emerges from the
sellerβs attempt to reduce the incentives of the high-type customer to select the contract meant for the low type.
β The seller also achieves self-selection by setting an attractive output for the low-type buyer, i.e., πππΏπΏ is lower than under complete information.
Advanced Microeconomic Theory 90
Price Discrimination: Second-degree
β’ Example:β Consider a monopolist selling a textbook to two
types of graduate students, low- and high-demand, with utility function
ππππ(ππππ ,πΉπΉππ) = ππππ2
2β ππππππππ β πΉπΉππ
where ππ = {π·π·,π»π»} and πππ»π» > πππΏπΏ. β Hence, the UMP of type ππ student is
maxππππ
ππππ2
2β ππππππππ β πΉπΉππ s. t. ππππππ + πΉπΉππ β€ π€π€ππ
where π€π€ππ > 0 denotes the studentβs wealth.Advanced Microeconomic Theory 91
Price Discrimination: Second-degree
β’ Example (continued):β By Walrasβ law, the constraint binds
πΉπΉππ = π€π€ππ β ππππππβ Then, the UMP can be expressed as
maxππππ
ππππ2
2β ππππππππ β (π€π€ππ β ππππππ)
β FOCs wrt ππππ yields the direct demand function: ππππ β ππππ + ππ = 0 or ππππ = ππππ β ππ
Advanced Microeconomic Theory 92
Price Discrimination: Second-degree
β’ Example (continued):β Assume that the proportion of high-demand (low-
demand) students is πΎπΎ (1 β πΎπΎ, respectively).
β The monopolistβs constant marginal cost is ππ > 0, which satisfies ππππ > ππ for all ππ = {π·π·,π»π»}.
β Consider for simplicity that πππΏπΏ > πππ»π»+ππ2
.
β This implies that each type of student would buy the textbook, both when the firm practices uniform pricing and when it sets two-part tariffs Exercise.
Advanced Microeconomic Theory 93
Advertising in Monopoly
Advanced Microeconomic Theory 94
Advertising in Monopoly
β’ Advertising: non-price strategy to capture surplus
β’ The monopolist must balance the additional demand that advertising entails and its associated costs (π΄π΄ dollars)
β’ The monopolist solvesmaxπ΄π΄
ππ οΏ½ ππ ππ,π΄π΄ β ππππ ππ ππ,π΄π΄ β π΄π΄
where the demand function ππ ππ,π΄π΄ depends on price and advertising.
Advanced Microeconomic Theory 95
Advertising in Monopolyβ’ Taking FOCs with respect to π΄π΄,
ππ οΏ½ ππππ ππ,π΄π΄πππ΄π΄
β οΏ½ππππππππππππππ
οΏ½ ππππ ππ,π΄π΄πππ΄π΄
β 1 = 0
Rearranging, we obtain
ππ βππππ ππππ ππ,π΄π΄πππ΄π΄
= 1β’ Let us define the advertising elasticity of demand
ππππ,π΄π΄ = % increse in ππ% increse in π΄π΄
= ππππ ππ,π΄π΄πππ΄π΄
οΏ½ π΄π΄ππ
Or, rearranging,
ππππ,π΄π΄ οΏ½πππ΄π΄
= ππππ ππ,π΄π΄πππ΄π΄
Advanced Microeconomic Theory 96
Advertising in Monopoly
β’ We can then rewrite the above FOC as
ππ βππππ ππππ,π΄π΄ οΏ½πππ΄π΄
ππππ ππ,π΄π΄πππ΄π΄
= 1
β’ Dividing both sides by ππππ,π΄π΄ and rearranging
ππ βππππ = 1ππππ,π΄π΄
οΏ½ π΄π΄ππ
β’ Dividing both sides by ππππβππππππ
= 1ππππ,π΄π΄
οΏ½ π΄π΄πποΏ½ππ
Advanced Microeconomic Theory 97
Advertising in Monopoly
β’ From the Lerner index, we know that ππβππππππ
= β 1ππππ,ππ
. Hence,
β 1ππππ,ππ
= 1ππππ,π΄π΄
οΏ½ π΄π΄πποΏ½ππ
β’ And rearranging
βππππ,π΄π΄
ππππ,ππ= π΄π΄
πποΏ½ππβ The right-hand side represents the advertising-to-sales
ratio.β For two markets with the same ππππ,ππ, the advertising-to-
sales ratio must be larger in the market where demand is more sensitive to advertising (higher ππππ,π΄π΄).
Advanced Microeconomic Theory 98
Advertising in Monopoly
β’ Example: β If the price-elasticity in a given monopoly market
is ππππ,ππ = β1.5 and the advertising-elasticity is ππππ,π΄π΄ = 0.1, the advertising-to-sales ratio should be
π΄π΄πποΏ½ππ
= β 0.1β1.5
= 0.067
β Advertising should account for 6.7% of this monopolistβs revenue.
Advanced Microeconomic Theory 99
Regulation of Natural Monopolies
Advanced Microeconomic Theory 100
Regulation of Natural Monopolies
β’ Natural monopolies: Monopolies that exhibit decreasing cost structures, with the MC curve lying below the AC curve.
β’ Hence, having a single firm serving the entire market is cheaper than having multiple firms, as aggregate average costs for the entire industry would be lower.
Advanced Microeconomic Theory 101
Regulation of Natural Monopoliesβ’ Unregulated natural
monopolist maximizes profits at the point where MR=MC, producing ππ1units and selling them at a price ππ1.
β’ Regulated natural monopolist will charge ππ2(where demand crosses MC) and produce ππ2units.
β’ The production level ππ2implies a loss of ππ2 β ππ2per unit.
Advanced Microeconomic Theory 102
Regulation of Natural Monopolies
β’ Dilemma with natural monopolies:β abandon the policy of setting prices equal to
marginal cost, ORβ continue applying marginal cost pricing but
subsidize the monopolist for his lossesβ’ Solution to the dilemma:
β A multi-price system that allows for price discrimination
β Charging some users a high price while maintaining a low price to other users
Advanced Microeconomic Theory 103
Regulation of Natural Monopolies
β’ Multi-price system: β a high price ππ1β a low price ππ2
β’ Benefit: (ππ1 β ππ1) per unit in the interval from 0 to ππ1
β’ Loss: (ππ2 β ππ2) per unit in the interval (ππ2 β ππ1)
β’ The monopolist price discriminates iff
ππ1 β ππ1 ππ1 >(ππ2 β ππ2)(ππ2 β ππ1)
Advanced Microeconomic Theory 104
Regulation of Natural Monopolies
β’ An alternative regulation:β allow the monopolist to charge a price above
marginal cost that is sufficient to earn a βfairβ rate of return on capital investments
β’ Two difficulties:β what is a βfairβ rate of returnβ overcapitalization
Advanced Microeconomic Theory 105
Regulation of Natural Monopolies
β’ Overcapitalization of natural monopolies:β Suppose a production function of the form ππ =ππ(ππ, ππ). An unregulated monopoly with profit function ππππ ππ, ππ β π€π€ππ β ππππ has a rate of return on capital, ππ. Suppose furthermore that the rate of return on capital investments, ππ, is constrained by a regulatory agency to be equal to ππ0.
Advanced Microeconomic Theory 106
Regulation of Natural Monopolies
β’ PMP:π·π· = ππππ ππ, ππ β π€π€ππ β ππππ
+ππ π€π€ππ + ππ0ππ β ππππ(ππ, ππ)where 0 < ππ < 1.
β’ FOCs:πππΏπΏπππ‘π‘
= πππππ‘π‘ β π€π€ + ππ π€π€ β πππππ‘π‘ = 0πππΏπΏππππ
= ππππππ β ππ + ππ ππ0 β ππππππ = 0πππΏπΏππππ
= π€π€ππ + ππ0ππ β ππππ ππ, ππ = 0Advanced Microeconomic Theory 107
Regulation of Natural Monopolies
β’ From the first FOC:πππππ‘π‘ = π€π€
β’ From the second FOC:1 β ππ ππππππ = ππ β ππππ0
and rearranging
ππππππ = ππβππππ01βππ
= ππ β ππ(ππ0βππ)1βππ
β Since ππ0 > ππ and 0 < ππ < 1, then ππππππ < ππ.β Hence, the firm would hire more capital than under
unregulated condition, where ππππππ = ππ.Advanced Microeconomic Theory 108
Regulation of Natural Monopoliesβ’ ππππππ is the value of the
marginal product of capitalβ It is decreasing in ππ (due to
diminishing marginal return, i.e., ππππππ < 0)
β’ ππ and ππ β ππ(ππ0βππ)1βππ
are the marginal cost of additional units of capital in the unregulated and regulated monopoly, respectively
ππ > ππ β ππ(ππ0βππ)1βππ
β’ Example: electricity and water suppliers
Advanced Microeconomic Theory 109
Regulation of Natural Monopoliesβ’ An alternative illustration
of the overcapitalization (Averch-Johnson effect)
β’ Before regulation, the firm selects (π·π·π΅π΅ππ ,πΎπΎπ΅π΅ππ)
β’ After regulation, the firm selects (π·π·π΄π΄ππ ,πΎπΎπ΄π΄ππ), where πΎπΎπ΄π΄ππ > πΎπΎπ΅π΅ππ but π·π·π΄π΄ππ < π·π·π΅π΅ππ
β’ The overcapitalization result only captures the substitution effect of a cheaper input.β Output effect?
Advanced Microeconomic Theory 110
Monopsony
Advanced Microeconomic Theory 111
Monopsony
β’ Monopsony: A single buyer of goods and services exercises βbuying powerβ by paying prices below those that would prevail in a perfectly competitive context.
β’ Monopsony (single buyer) is analogous to that of a monopoly (single seller).
β’ Examples: a coal mine, Walmart Superstore in a small town, etc.
Advanced Microeconomic Theory 112
Monopsony
β’ Consider that the monopsony faces competition in the product market, where prices are given at ππ > 0, but is a monopsony in the input market (e.g., labor services).
β’ Assume an increasing and concave production function, i.e., ππβ² π₯π₯ > 0 and ππβ²β² π₯π₯ β€ 0.β This yields a total revenue of ππππ π₯π₯ .
β’ Consider a cost function π€π€ π₯π₯ οΏ½ π₯π₯, where π€π€(π₯π₯) denotes the inverse supply function of labor π₯π₯. β Assume that π€π€β² π₯π₯ > 0 for all π₯π₯.β This indicates that, as the firm hires more workers, labor
becomes scarce, thus increasing the wages of additional workers.
Advanced Microeconomic Theory 113
Monopsony
β’ The monopsony PMP is maxπ₯π₯
ππππ π₯π₯ β π€π€ π₯π₯ π₯π₯β’ FOC wrt the amount of labor services π₯π₯ yields
ππππβ² π₯π₯β β π€π€ π₯π₯β β π€π€β² π₯π₯β π₯π₯β = 0βΉ ππππβ² π₯π₯β
π΄π΄= π€π€ π₯π₯β + π€π€β² π₯π₯β π₯π₯β
π΅π΅β π΄π΄: βmarginal revenue productβ of labor.β π΅π΅: βmarginal expenditureβ (ME) on labor. The additional worker entails a monetary outlay of π€π€ π₯π₯β . Hiring more workers make labor become more scarce,
ultimately forcing the monopsony to raise the prevailing wage on all inframarginal workers, as captured by π€π€β² π₯π₯β π₯π₯β.
Advanced Microeconomic Theory 114
Monopsony
β’ Monopsonist hiring and salary decisions.
Advanced Microeconomic Theory 115
β The marginal revenue product of labor, ππππβ² π₯π₯ , is decreasing in π₯π₯ given that ππβ²β² π₯π₯ β€ 0.
β The labor supply, π€π€ π₯π₯ , is increasing in π₯π₯ since π€π€β²(π₯π₯) > 0.
β The marginal expenditure (ME) on labor lies above the supply function w π₯π₯since π€π€β² π₯π₯ > 0.
β The monopsony hires π₯π₯βworkers at a salary of π€π€ π₯π₯β .
Monopsony
β’ A deadweight loss from monopsony is
π·π·π·π·π·π· = β«π₯π₯βπ₯π₯ππππ ππππβ² π₯π₯ β π€π€ π₯π₯ πππ₯π₯
β’ That is, the area below the marginal revenue product and above the supply curve, between π₯π₯β and π₯π₯ππππworkers.
Advanced Microeconomic Theory 116
Monopsony
β’ We can write the monopsony profit-maximizing condition, i.e., ππππβ² π₯π₯β = π€π€ π₯π₯β + π€π€β² π₯π₯β π₯π₯β, in terms of labor supply elasticity, using the following steps:
ππππβ² π₯π₯β = π€π€ π₯π₯β + ππππ π₯π₯β
πππ₯π₯βπ₯π₯β
= π€π€ π₯π₯β 1 + ππππ π₯π₯β
πππ₯π₯βπ₯π₯β
ππ π₯π₯ββ’ And rearranging,
ππππβ² π₯π₯β = π€π€ π₯π₯β 1 + 1πππ₯π₯βππππ
ππ π₯π₯βπ₯π₯β
Advanced Microeconomic Theory 117
Monopsony
β’ Since πππ₯π₯β
ππππππ π₯π₯β
π₯π₯βrepresents the elasticity of labor
supply ππ, then
ππππβ² π₯π₯β = π€π€ π₯π₯β 1 + 1ππ
β’ Intuitively, as ππ β β (labor supply becoming perfectly elastic), the behavior of the monopsonist approaches that of a pure competitor.
Advanced Microeconomic Theory 118
Monopsony
β’ The equilibrium condition above is also sufficient as long as
ππππβ²β² π₯π₯β β 2π€π€β² π₯π₯β β π€π€β²β² π₯π₯β π₯π₯β < 0
β’ Since ππβ²β² π₯π₯β < 0, π€π€β² π₯π₯β > 0 (by assumption), we only need that either:
a) the supply function is convex, i.e., π€π€β²β²(π₯π₯β) > 0; or
b) if it is concave, i.e., π€π€β²β² π₯π₯β < 0, its concavity is not very strong, that is
ππππβ²β² π₯π₯β β 2π€π€β² π₯π₯β < π€π€β²β² π₯π₯β π₯π₯β
Advanced Microeconomic Theory 119
Monopsony
β’ Example:β Consider a monopsonist with production function ππ π₯π₯ = πππ₯π₯, where ππ > 0, and facing a given market price ππ > 0 per unit of output.
β Labor supply is π€π€ π₯π₯ = πππ₯π₯, where ππ > 0. β The marginal revenue product of hiring an
additional worker isππππβ² π₯π₯ = ππππ
β The marginal expenditure on labor isπ€π€ π₯π₯ + π€π€β² π₯π₯ π₯π₯ = πππ₯π₯ + πππ₯π₯ = 2πππ₯π₯
Advanced Microeconomic Theory 120
Monopsony
β’ Example (continued):β Setting them equal to each other, ππππ = 2πππ₯π₯β,
yields a profit-maximizing amount of labor:
π₯π₯β =ππππ2ππ
β π₯π₯β increases in the price of output, ππ, and in the marginal productivity of labor, ππ; but decreases in the slope of labor supply, ππ.
β Sufficiency holds sinceππππβ²β² π₯π₯β β 2π€π€β² π₯π₯β = πππ β 2ππ < 0 = π€π€β²β² π₯π₯β π₯π₯β
Advanced Microeconomic Theory 121