10 - 1 The Aggregate Expenditures Model 10 C H A P T E R.

10 - 1

The Aggregate Expenditures Model

10 C H A P T E R

10 - 2

Simplifying Assumptions for the Private Closed-Economy model

Assumptions: A closed economy with no international trade (no

exports or imports). Government is ignored (no government purchases and

no taxes). Although both households and businesses save, we

assume here that all saving is personal. Depreciation and net foreign income are assumed to be

zero for simplicity. The economy has excess production capacity, so an

increase in AD will raise output and employment, but not prices.

10 - 3

Two reminders concerning the assumptions:

1. They leave out two key components of aggregate demand (government spending and foreign trade), because they are largely affected by influences outside the domestic market system.

2. With no government or foreign trade, GDP, national income (NI), personal income (PI), and disposable income (DI) are all the same.

10 - 4

Tools of Aggregate Expenditures Theory: Consumption and Investment Schedules

The theory assumes that the level of output and employment depend directly on the level of aggregate expenditures. Changes in output reflect changes in aggregate spending.

In a closed private economy the two components of aggregate expenditures are:– Consumption (C). – Gross investment (Ig).

10 - 5

Investment Schedule: The relationship between investment and GDP

shows the amounts business firms collectively intend to invest at each possible level of GDP or DI.

In developing the investment schedule, it is assumed that investment is independent of the current income.

The assumption that investment is independent of income is a simplification, but it will be used here.

10 - 6

Model Simplifications

• Investment demand vs. schedule r

an

d i (

per

cen

t)

Investment (billions of dollars)

ID

20

8

Real GDP (billions of dollars)

20

Inve

stm

ent

(bil

lion

s of

dol

lars

)

Ig

Investment Demand Curve Investment Schedule

2020

Investment Demand Curve

Investment Schedule

10 - 7

Equilibrium GDP: Expenditures-Output Approach

Recall that consumption level is directly related to the level of income and that here income is equal to output level.

Investment is independent of income here and is planned or intended regardless of the current income situation.

Equilibrium GDP is the level of output whose production will create total spending just sufficient to purchase that output. Otherwise there will be a disequilibrium situation.

10 - 828-8

(1) 40

(2) 45

(3) 50

(4) 55

(5) 60

(6) 65

(7) 70

(8) 75

(9) 80

(10) 85

$375

390

405

420

435

450

465

480

495

510

$-5

0

5

10

15

20

25

30

35

40

20

20

20

20

20

20

20

20

20

20

$395

410

425

440

455

470

485

500

515

530

$-25

-20

-15

-10

-5

0

+5

+10

+15

+20

Increase

Increase

Increase

Increase

Increase

Equilibrium

Decrease

Decrease

Decrease

Decrease

$370

390

410

430

450

470

490

510

530

550

(2)Real

DomesticOutput

(andIncome)

(GDP=DI)

(3)Con-

sump-tion(C)

(4)Saving (S)

(1) – (2)

(5)Investment

(Ig)

(6)Aggregate

Expenditures(C+Ig)

(7)UnplannedChanges inInventories

(+ or -)

(8)Tendency ofEmployment,Output, and

Income

(1)Employ-

ment

…in Billions of Dollars

Equilibrium GDP

In millions

10 - 9

At levels below equilibrium, businesses will adjust to excess demand (revealed by the declining inventories) by stepping up production. They will expand production at any level of GDP less than the $470 billion equilibrium. As GDP rises, the number of jobs and total income will also rise

At levels of GDP above equilibrium, aggregate expenditures will be less than GDP. Businesses will have unsold output (Unplanned inventory investment) and will cut back on the rate of production. As GDP declines, the number of jobs and total income will also decline, but eventually the GDP and aggregate spending will be in equilibrium at $470 billion.

10 - 10

Pri

vate

sp

end

ing

, C +

I g

(bill

ion

s o

f d

olla

rs)

o45

o

C

C + Ig

Ig = $20 Billion

Equilibrium

Real domestic product, GDP (billions of dollars)

370 390 410 430 450 470 490 510 530 550

(C + Ig = GDP)

EQUILIBRIUM GDP

C =$450 Billion

$530

510

490

470

450

430

410

390

370

10 - 11

EQUILIBRIUM GDP

At equilibrium, saving (leakage) and Planned Investment (injection) are Equal:Leakage = Injection (S) = (I)

orNo Unplanned Changes in Inventories (Unplanned

inventory = 0)Disequilibrium

Above EquilibriumLeakage (S) > Injection (I)• Unplanned inventory accumulation

10 - 12

Below Equilibrium Leakage (S) < Injection (I)

Unplanned inventory depletion

Saving represents a “leakage” from spending stream and causes (C) to be less than GDP.

Some of output is planned for business investment and not consumption, so this investment spending can replace the leakage due to saving.

10 - 13

Unplanned expendituresThe unplanned portion is reflected as a business expenditure,

even though the business may not have desired it, because the total output has a value that belongs to someone - either as a planned purchase or as an unplanned inventory.

1. If aggregate spending is less than equilibrium GDP, then businesses will find themselves with unplanned inventory investment on top of what was already planned.

2. If aggregate expenditures exceed GDP, then there will be less inventory investment than businesses planned as businesses sell more than they expected. This is reflected as a negative amount of unplanned investment in inventory.

3. At equilibrium there are no unplanned changes in inventory.

10 - 14

Quick Review

Equilibrium GDP is where aggregate expenditures equal real domestic output: C + planned Ig = GDP

A difference between saving and planned investment causes a difference between the production and spending plans of the economy as a whole.

A difference between production and spending plans leads to unintended inventory investment or unintended decline in inventories.

As long as unplanned changes in inventories occur, businesses will revise their production plans upward or downward until the investment in inventory is equal to what they planned.

Only where planned investment and saving are equal there will be no unintended investment or disinvestment in inventories to drive the GDP down or up.

10 - 15

Changes in Equilibrium GDP and the Multiplier

An initial change in spending (caused by shifts in C and I) will be acted on by the multiplier to produce larger changes in output.

The “initial change” is in planned investment spending. It could also result from a non-income-induced changes in consumption.

Impact of changes in investment. Suppose investment spending rises by 5 billion (due to a rise in

expected rate of return or to a decline in interest rates).1. The increase in aggregate expenditures from investment

leads to an increase in equilibrium GDP (size depends on the multiplier).

2. Conversely, a decline in investment spending leads to a decrease in equilibrium GDP (size depends on the multiplier).

10 - 16

CHANGES IN EQUILIBRIUM GDPAND THE MULTIPLIER

Pri

vate

sp

end

ing

(b

illio

ns

of

do

llars

)

o45

o


510

490

470

450

430

430 450 470 490 510

(C + Ig ) 0

(C + Ig ) 1

Equilibrium GDPat Ig0 level of investment


Increasesin the levelof C + Ig

10 - 17

CHANGES IN EQUILIBRIUM GDPAND THE MULTIPLIER

Pri

vate

sp

end

ing

(b

illio

ns

of

do

llars

)

o45

o


510

490

470

450

430

430 450 470 490 510


(C + Ig ) 0

(C + Ig ) 2

Decreasesin the levelof C + Ig

10 - 18

International Trade and Equilibrium Output

Net exports affect aggregate expenditures in an open economy. Exports expand aggregate spending and imports contract aggregate spending on domestic output.

Exports (X) create domestic production, income, and employment due to foreign spending on domestically produced goods and services.

Imports (M) reduce the sum of consumption and investment expenditures by the amount expended on imported goods, so this figure must be subtracted so as not to overstate aggregate expenditures on domestically produced goods and services.

10 - 19

The net export schedule Shows hypothetical amount of net exports that will

occur at each level of GDP. Note that we assume that net exports are independent of the current GDP level.

Positive net exports increase aggregate expenditures beyond what they would be in a closed economy and thus have an expansionary effect. The multiplier effect also is at work.

Negative net exports decrease aggregate expenditures beyond what they would be in a closed economy and thus have a contractionary effect. The multiplier effect also is at work here.

10 - 2028-20

RealGDP

+5

0

-5

Net

Exp

orts

Xn

(bil

lion

s of

Dol

lars

)

Real GDP (billions of dollars)

Agg

rega

te E

xpen

dit

ure

s(b

illi

ons

of d

olla

rs)

510

490

470

450

43045°

430 450 470 490 510

Net Exports and Equilibrium GDP

AggregateExpenditureswith PositiveNet Exports

C + Ig

AggregateExpenditureswith NegativeNet Exports

C + Ig+Xn2

C + Ig+Xn1

Xn1

Xn2

Positive Net Exports

Negative Net Exports

450 470 490

10 - 21

International economic linkages

1. Prosperity abroad: generally raises our exports and transfers some of their prosperity to us. (Conversely, recession abroad has the reverse effect.)

2. Tariffs on Kuwaiti products: may reduce our exports and depress our economy, causing us to retaliate and worsen the situation.

3. Changes in exchange rates: Depreciation of the KD lowers the cost of Kuwaiti goods

to foreigners and encourages exports from Kuwait, while discouraging the purchase of imports in Kuwait. This could lead to higher real GDP or to inflation, depending on the domestic employment situation.

Appreciation of the KD could have the opposite impact.

10 - 2228-22

-700 200 150 100 50 0 50 100 150 200 250

Net Exports of GoodsSelect Nations, 2006

Positive Net ExportsNegative Net Exports

Canada

France

Japan

Italy

Germany

United Kingdom

United States

+31

+70

+203

-45

-27

-171

-881

Source: World Trade Organization

10 - 23

Adding the Public SectorSimplifying assumptions:

1. Simplified investment and net export schedules are used. Assume they are independent of the level of current GDP.

2. Assume government purchases do not impact private spending schedules.

3. Assume that net tax revenues are derived entirely from personal taxes so that GDP, NI, and PI remain equal.

4. Assume that tax collections are independent of GDP level (i.e., it is a lump-sum tax)

5. The price level is assumed to be constant unless otherwise indicated.

10 - 24

Impact of government spending Increases in government spending boost aggregate

expenditures. It is subject to the multiplier effect.

Impact of Taxes Taxes reduce DI and, therefore, consumption and

saving at each level of GDP. An increase in taxes will lower the aggregate

expenditures schedule relative to the 45-degree line and reduce the equilibrium GDP, and a decrease in tax will do the opposite.

At equilibrium GDP, the sum of leakages equals the sum of injections, i.e.,

Saving + Imports + Taxes = Investment + Exports + Government Purchases.

(leakage) = (injection)

10 - 25

Adding the Public Sector

(1) $370

(2) 390

(3) 410

(4) 430

(5) 450

(6) 470

(7) 490

(8) 510

(9) 530

(10) 550

$375

390

405

420

435

450

465

480

495

510

$-5

0

5

10

15

20

25

30

35

40

$20

20

20

20

20

20

20

20

20

20

10

10

10

10

10

10

10

10

10

10

20

20

20

20

20

20

20

20

20

20

$415

430

445

460

475

490

505

520

535

550

10

10

10

10

10

10

10

10

10

10

(1)Level ofOutput

andIncome

(GDP=DI)

(2)Consump-

tion(C)

(3)Saving (S)

(4)Investment

(Ig)

(5)Net Exports

(Xn) (6)Government

(G)

(7)Aggregate

Expenditures(C+Ig+Xn+G)(2)+(4)+(5)+(6)

Exports(X)

Imports(M)

…in Billions of Dollars

10 - 26

ADDING THE PUBLIC SECTOR

Ag

gre

gat

e E

xpen

dit

ure

s (b

illio

ns

of

do

llars

)

o45

o


470 550

C

C + Ig + Xn

C + Ig + Xn + GGovernmentSpending of$20 Billion

Government Purchases and Equilibrium GDP

10 - 27

ADDING THE PUBLIC SECTORLump-Sum Tax and Equilibrium GDP

Ag

gre

gat

e E

xpen

dit

ure

s (b

illio

ns

of

do

llars

)

o45

o


490 550

C + Ig + Xn + G

Ca + Ig + Xn + G

$15 Billion Decreasein Consumption froma $20 Billion Increasein Taxes

10 - 28

Government purchases and taxes have different impacts.

Equal additions in government spending and taxation increase the equilibrium GDP.

a. If G and T are each increased by a particular amount, the equilibrium level of real output will rise by that same amount.

b. Example, an increase of $20 billion in G and an offsetting increase of $20 billion in T will increase equilibrium GDP by $20 billion.

10 - 29

Explanationa. An increase in G is direct and adds $20 billion to

aggregate expenditures.b. An increase in T has an indirect effect on aggregate

expenditures because T reduces disposable incomes first, and then C falls by the amount of the tax times MPC.

c. The overall result is a rise in initial spending of $20 billion minus a fall in initial spending of $15 billion (.75 x $20 billion), which is a net upward shift in aggregate expenditures of $5 billion.

d. When this is subject to the multiplier effect, which is 4 (MPC =.75) in this example, the increase in GDP will be equal to $4 × $5 billion or $20 billion, which is the size of the change in G.

10 - 30

Injections, Leakages, and Unplanned Changes in Inventories – Equilibrium revisited

As demonstrated earlier, in a closed private economy equilibrium occurs when saving (a leakage) equals planned investment (an injection).

With the introduction of a foreign sector (net exports) and a public sector (government), new leakages and injections are introduced.

1. Imports and taxes are added leakages.

2. Exports and government purchases are added injections.

10 - 31

Equilibrium is found when the leakages equal the injections. When leakages equal injections, there are no unplanned changes in inventories.

Symbolically, equilibrium occurs when:

Sa + M + T = Ig + X + G

where Sa is after-tax saving, M is imports, T is taxes, Ig is (gross) planned investment, X is exports, and G is government purchases.

10 - 32

Equilibrium vs. Full-Employment GDP A recessionary expenditure gap exists when

equilibrium GDP is below full-employment GDP.

A recessionary gap is the amount by which aggregate expenditures fall short of those required to achieve the full-employment level of GDP, or the amount by which the schedule would have to shift upward to realize the full-employment GDP.

The effect of the recessionary gap is to pull down the prices of the economy’s output.

10 - 33

An inflationary gap exists when aggregate expenditures exceed full-employment GDP, it exists when aggregate spending exceeds what is necessary to achieve full employment.

The inflationary gap is the amount by which the aggregate expenditures schedule must shift downward to realize the full-employment noninflationary GDP.

The effect of the inflationary gap is to pull up the prices of the economy’s output.

10 - 34

FULL-EMPLOYMENT GDP

Ag

gre

gat

e E

xpen

dit

ure

s (b

illio

ns

of

do

llars

)

o45

o


490 510 530

AE0

Recessionary Gap

AE1

530

510

490

Recessionary Gap= $5 Billion

Full Employment

10 - 35

FULL-EMPLOYMENT GDP

Ag

gre

gat

e E

xpen

dit

ure

s (b

illio

ns

of

do

llars

)

o45

o


490 510 530

AE0

Inflationary Gap

AE2

530

510

490

Inflationary Gap= $5 Billion

Full Employment

10 - 36

Last Word: Say’s Law, The Great Depression, and Keynes

Until the Great Depression of the 1930, most economists going back to Adam Smith had believed that a market system would ensure full employment of the economy’s resources except for temporary, short-term upheavals.

If there were deviations, they would be self-correcting. A slump in output and employment would reduce prices, which would increase consumer spending; would lower wages, which would increase employment again; and would lower interest rates, which would expand investment spending.

10 - 37

• Say’s law, attributed to the French economist J. B. Say in the early 1800s, summarized the view in a few words: “Supply creates its own demand.”

• Say’s law is easiest to understand in terms of barter. The woodworker produces furniture in order to trade for other needed products and services. All the products would be traded for something, or else there would be no need to make them. Thus, supply creates its own demand.

• The Great Depression of the 1930s was worldwide. GDP fell by 40 percent in U.S. and the unemployment rate rose to nearly 25 percent. The Depression seemed to refute the classical idea that markets were self-correcting and would provide full employment.

10 - 38

John Maynard Keynes in 1936 in his General Theory of Employment, Interest, and Money, provided an alternative to classical theory, which helped explain periods of recession.

Not all income is always spent, contrary to Say’s law.

Producers may respond to unsold inventories by reducing output rather than cutting prices.

A recession or depression could follow this decline in employment and incomes.

10 - 1 The Aggregate Expenditures Model 10 C H A P T E R.

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