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10 - 1
The Aggregate Expenditures Model
9C H A P T E R
10 - 2
Simplifying Assumptions for the Private Closed-Economy model
Assumptions:• We first assume 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.
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• There are two reminders concerning these 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).
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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.
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INVESTMENT DEMAND & SCHEDULE
Exp
ecte
d r
ate
of
retu
rn,
r, a
nd
real
in
tere
st r
ate,
i (
per
cen
ts)
Inve
stm
ent
(bil
lio
ns
of
do
lla
rs)
Investment(billions of dollars)
20
8
20
Real Domestic Product, GDP(billions of dollars)
I D
Ig
InvestmentDemandCurve
InvestmentSchedule
2020
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.
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Equilibrium GDP: Expenditures-Output Approach
Empl. GDP C S I C+I
(Ag.Exp) Unpl.
Invent.
Empl. Output Income
40 370 375 -5 20 395 -25 + 45 390 390 0 20 410 -20 + 50 410 405 5 20 425 -15 + 55 430 420 10 20 440 -10 + 60 450 435 15 20 455 -5 + 65 470 450 20 20 470 0 Equilib. 70 490 465 25 20 485 5 - 75 510 480 30 20 500 10 - 80 530 495 35 20 515 15 - 85 550 510 40 20 530 20 -
Unplanned change in inventories
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• 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.
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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 + I g = GDP)
EQUILIBRIUM GDP
C =$450 Billion
$530
510
490
470
450
430
410
390
370
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EQUILIBRIUM GDP
At equilibrium, saving (leakage) and Planned Investment (injection) are Equal:Leakage = Injection (S) (I)
orNo Unplanned Changes in Inventories (Unplanned
inventory = 0)
• Above EquilibriumLeakage (S) > Injection (I)• Unplanned inventory accumulation
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Disequilibrium
• Below EquilibriumLeakage (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.
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Unplanned expenditures
• The 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.
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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.
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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).
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CHANGES IN EQUILIBRIUM GDPAND THE MULTIPLIER
Pri
vate
sp
end
ing
(b
illio
ns
of
do
llars
)
o45
o
Real domestic product, GDP (billions of dollars)
510
490
470
450
430
430 450 470 490 510
(C + Ig ) 0
(C + Ig ) 1
Equilibrium GDPat Ig0 level of investment
Equilibrium GDPat Ig1 level of investment
Increasesin the levelof C + Ig
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CHANGES IN EQUILIBRIUM GDPAND THE MULTIPLIER
Pri
vate
sp
end
ing
(b
illio
ns
of
do
llars
)
o45
o
Real domestic product, GDP (billions of dollars)
510
490
470
450
430
430 450 470 490 510
Equilibrium GDPat Ig2 level of investment
(C + Ig ) 0
(C + Ig ) 2
Decreasesin the levelof C + Ig
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International Trade and Equilibrium Output
• Net exports (exports minus imports) affect aggregate expenditures in an open economy. Exports expand aggregate spending and imports contract aggregate spending on domestic output.
1. Exports (X) create domestic production, income, and employment due to foreign spending on Kuwait’s produced goods and services.
2. 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 Kuwait’s produced goods and services.
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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.
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INTERNATIONAL TRADE AND AGGREGATE EXPENDITURES
Pri
vate
sp
end
ing
(b
illi
on
s o
f d
oll
ars)
o45o
Real domestic product, GDP (billions of dollars)
510
490
470
450
430
430 450 470 490 510
Aggregate Expenditureswith Positive Net Exports
C + Ig
C + Ig + Xn1
Net
Exp
ort
s, X
n
(bil
lio
ns
of
do
lla
rs)
+5
0
-5
430 450 470 490 510 Real GDP
Net exports schedule
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INTERNATIONAL TRADE AND AGGREGATE EXPENDITURES
Pri
vate
sp
end
ing
(b
illi
on
s o
f d
oll
ars)
o45o
Real domestic product, GDP (billions of dollars)
510
490
470
450
430
430 450 470 490 510
Aggregate Expenditureswith Negative Net Exports
C + Ig C + Ig + Xn2
Net
Exp
ort
s, X
n
(bil
lio
ns
of
do
lla
rs)
+5
0
-5
430 450 470 490 510 Real GDP
Net exports schedule
10 - 22
International economic linkages
Circumstances or policies abroad affect domestic GDP
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 or appreciation.
– 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 - 23
GLOBAL PERSPECTIVENET EXPORTS OF GOODS, 2001
Source: World Trade Organization
-400 -140 -100 -60 -20 0 20 60 100
Negative Net Exports Positive Net Exports
Billions of Dollars
United States
United Kingdom
Canada
France
Germany
Italy
Japan
10 - 24
Adding the Public SectorSimplifying assumptions:
1. Simplified investment and net export schedules are used. We assume they are independent of the level of current GDP.
2. We assume government purchases do not impact private spending schedules.
3. We assume that net tax revenues are derived entirely from personal taxes so that GDP, NI, and PI remain equal. DI is PI minus net personal taxes.
4. We 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.
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Impact of government spending 1. Increases in government spending boost aggregate
expenditures.
2. Government spending is subject to the multiplier.
Impact of Taxes:
1. Taxes reduce DI and, therefore, consumption and saving at each level of GDP.
2. 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.
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• At equilibrium GDP, the sum of leakages equals the sum of injections, i.e.,
Saving + Imports + Taxes = Investment + Exports + Gov’t Purch.
(leakage) = (injection)
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GDP(DI) C S I X M G AE(C+I+Xn+G) 370 375 -5 20 10 10 20 415 390 390 0 20 10 10 20 430 410 405 5 20 10 10 20 445 430 420 10 20 10 10 20 460 450 435 15 20 10 10 20 475 470 450 20 20 10 10 20 490 490 465 25 20 10 10 20 505 510 480 30 20 10 10 20 520 530 495 35 20 10 10 20 535 550 510 40 20 10 10 20 550 570 525 45 20 10 10 20 565
10 - 28
ADDING THE PUBLIC SECTOR
Ag
gre
gat
e E
xpen
dit
ure
s (b
illio
ns
of
do
llars
)
o45
o
Real domestic product, GDP (billions of dollars)
470 550
C
C + Ig + Xn
C + Ig + Xn + GGovernmentSpending of$20 Billion
Government Purchases and Equilibrium GDP
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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
Real domestic product, GDP (billions of dollars)
490 550
C + Ig + Xn + G
Ca + Ig + Xn + G
$15 Billion Decreasein Consumption froma $20 Billion Increasein Taxes
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• 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.
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Explanation
a. 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.
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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.
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• 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 - 34
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.
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• 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.
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FULL-EMPLOYMENT GDP
Ag
gre
gat
e E
xpen
dit
ure
s (b
illio
ns
of
do
llars
)
o45
o
Real domestic product, GDP (billions of dollars)
490 510 530
AE0
Recessionary Gap
AE1
530
510
490
Recessionary Gap= $5 Billion
Full Employment
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FULL-EMPLOYMENT GDP
Ag
gre
gat
e E
xpen
dit
ure
s (b
illio
ns
of
do
llars
)
o45
o
Real domestic product, GDP (billions of dollars)
490 510 530
AE0
Inflationary Gap
AE2
530
510
490
Inflationary Gap= $5 Billion
Full Employment
10 - 38
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.
• 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.”
10 - 39
• 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.
• 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.
