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Aggregate Demand
and AggregateSupply
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Short-Run Economic Fluctuations
Economic activity fluctuates from year to year. In most years production of goods and services
rises.
In some years normal growth does not occur,causing a recession.
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Short-Run Economic Fluctuations
A recession is a period of declining real
incomes, and rising unemployment.
A depression is a severe recession.
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THREE KEY FACTS ABOUTECONOMIC FLUCTUATIONS
Economic fluctuations are irregular and
unpredictable.
Fluctuations in the economy are often called the
business cycle.
Most macroeconomic variables fluctuate
together.
As output falls, unemployment rises.
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THREE KEY FACTS ABOUTECONOMIC FLUCTUATIONS
Most macroeconomic variables fluctuate
together.
Most macroeconomic variables that measure some
type of income or production fluctuate closelytogether.
Although many macroeconomic variables fluctuate
together, they fluctuate by different amounts.
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THREE KEY FACTS ABOUTECONOMIC FLUCTUATIONS
As output falls, unemployment rises.
Changes in real GDP are inversely related to
changes in the unemployment rate.
During times of recession, unemployment risessubstantially.
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The Basic Model of Economic Fluctuations
The Basic Model of Aggregate Demand and
Aggregate Supply
Economist use the model of aggregate demand and
aggregate supply to explain short-run fluctuationsin economic activity around its long-run trend.
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The Basic Model of Economic Fluctuations
The Basic Model of Aggregate Demand and
Aggregate Supply
The aggregate-demand curve shows the quantity of
goods and services that households, firms, and thegovernment want to buy at each price level.
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The Basic Model of Economic Fluctuations
The Basic Model of Aggregate Demand and
Aggregate Supply
The aggregate-supply curve shows the quantity of
goods and services that firms choose to produce andsell at each price level.
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Aggregate Demand and Aggregate Supply...
Quantity of
Output
Price
Level
0
Aggregate
supply
Aggregate
demand
Equilibrium
output
Equilibrium
price level
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THE AGGREGATE-DEMANDCURVE
The four components of GDP (Y) contribute to
the aggregate demand for goods and services.
Y = C + I + G + NX
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Figure The Aggregate-Demand Curve...
Quantity of
Output
Price
Level
0
Aggregate
demand
P
Y Y2
P2
1. A decrease
in the price
level . . .
2. . . . increases the quantity of
goods and services demanded.
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Why the Aggregate-Demand Curve IsDownward Sloping
The Price Level and Consumption: The Wealth
Effect
The Price Level and Investment: The Interest
Rate Effect
The Price Level and Net Exports: The
Exchange-Rate Effect
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Why the Aggregate-Demand Curve IsDownward Sloping
The Price Level and Consumption: The Wealth
Effect
A decrease in the price level makes consumers feel
more wealthy (real income increases), which in turnencourages them to spend more.
This increase in consumer spending means larger
quantities of goods and services demanded.
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Why the Aggregate-Demand Curve IsDownward Sloping
The Price Level and Investment: The InterestRate Effect
A lower price level reduces the interest rate
(because lower P means consumers need lesscurrency to buy things, so they keep more currency
in banks, more money in banks means they charge
less interest rate as they have large quantity with
them which they can lend) , which encouragesgreater spending on investment goods.
This increase in investment spending means a larger
quantity of goods and services demanded.
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Why the Aggregate-Demand Curve IsDownward Sloping
The Price Level and Net Exports: TheExchange-Rate Effect
When a fall in the India's price level causes India's
interest rates to fall, Indian rupees flow to countrywhere interest is higher (say USA) , demand for
dollars increase, the real exchange rate depreciates,
which stimulates India's net exports.
The increase in net export spending means a larger
quantity of goods and services demanded.
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Why the Aggregate-Demand Curve MightShift
The downward slope of the aggregate demandcurve shows that a fall in the price level raises
the overall quantity of goods and services
demanded. Many other factors, however, affect the quantity
of goods and services demanded at any given
price level. When one of these other factors changes, the
aggregate demand curve shifts.
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Why the Aggregate-Demand Curve MightShift
Shifts arising from
Consumption
Investment
Government Purchases
Net Exports
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Shifts in the Aggregate DemandCurve
Quantity ofOutput
PriceLevel
0
Aggregatedemand, D1
P1
Y1
D2
Y2
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THE AGGREGATE-SUPPLYCURVE
In the long run, the aggregate-supply curve isvertical.
In the short run, the aggregate-supply curve is
upward sloping.
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THE AGGREGATE-SUPPLYCURVE
The Long-Run Aggregate-Supply Curve
In the long run, an economys production of goods
and services depends on its supplies of labor,
capital, and natural resources and on the availabletechnology used to turn these factors of production
into goods and services.
The price level does not affect these variables in the
long run.
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Figure The Long-Run Aggregate-Supply Curve
Quantity of
Output
Natural rate
of output
Price
Level
0
Long-run
aggregate
supply
P2
1. A change
in the price
level . . .
2. . . . does not affect
the quantity of goodsand services supplied
in the long run.
P
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THE AGGREGATE-SUPPLYCURVE
The Long-Run Aggregate-Supply Curve
The long-run aggregate-supply curve is vertical at
the natural rate of output.
This level of production is also referred to aspotential output or full-employment output.
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Why the Long-Run Aggregate-Supply CurveMight Shift
Any change in the economy that alters thenatural rate of output shifts the long-run
aggregate-supply curve.
The shifts may be categorized according to thevarious factors in the classical model that affect
output.
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Why the Long-Run Aggregate-Supply CurveMight Shift
Shifts arising
Labor
Capital
Natural Resources
Technological Knowledge
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Figure Long-Run Growth and Inflation
Quantity of
OutputY1980
AD1980
AD1990
Aggregate
Demand,AD2000
Price
Level
0
Long-run
aggregate
supply,LRAS1980
Y1990
LRAS1990
Y2000
LRAS2000
P1980
1. In the long run,
technological
progress shiftslong-run aggregate
supply . . .4. . . . and
ongoing inflation.
3. . . . leading to growth
in output . . .
P1990
P2000
2. . . . and growth in the
money supply shifts
aggregate demand . . .
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Why the Aggregate-Supply Curve SlopesUpward in the Short Run
In the short run, an increase in the overall levelof prices in the economy tends to raise the
quantity of goods and services supplied.
A decrease in the level of prices tends to reducethe quantity of goods and services supplied.
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Figure The Short-Run Aggregate-Supply Curve
Quantity of
Output
PriceLevel
0
Short-run
aggregate
supply
1. A decrease
in the price
level . . .
2. . . . reduces the quantity
of goods and services
supplied in the short run.
Y
P
Y2
P2
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Why the Aggregate-Supply Curve SlopesUpward in the Short Run
The Misperceptions Theory
Changes in the overall price level temporarily
mislead suppliers about what is happening in the
markets in which they sell their output: A lower price level causes misperceptions about
relative prices.
These misperceptions induce suppliers to decrease the
quantity of goods and services supplied.
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Why the Aggregate-Supply Curve SlopesUpward in the Short Run
The Sticky-Wage Theory
Nominal wages are slow to adjust, or are sticky in
the short run:
Wages do not adjust immediately to a fall in the pricelevel.
A lower price level makes employment and production
less profitable.
This induces firms to reduce the quantity of goods andservices supplied.
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The Sticky-Price Theory
Prices of some goods and services adjust sluggishlyin response to changing economic conditions:
An unexpected fall in the price level leaves some firms
with higher-than-desired prices.
This depresses sales, which induces firms to reduce the
quantity of goods and services they produce.
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Why the Short-Run Aggregate-Supply CurveMight Shift
Shifts arising
Labor
Capital
Natural Resources.
Technology.
Expected Price Level.
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Why the Aggregate Supply Curve Might Shift
An increase in the expected price level reducesthe quantity of goods and services supplied and
shifts the short-run aggregate supply curve to
the left. A decrease in the expected price level raises the
quantity of goods and services supplied and
shifts the short-run aggregate supply curve tothe right.
Fi Th L R E ilib i
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Figure The Long-Run Equilibrium
Natural rate
of output
Quantity of
Output
Price
Level
0
Short-run
aggregate
supply
Long-run
aggregate
supply
Aggregate
demand
AEquilibrium
price
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Fi C t ti i A t D d
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Figure Contraction in Aggregate Demand
Quantity of
Output
PriceLevel
0
Short-run aggregate
supply,AS
Long-run
aggregate
supply
Aggregate
demand,AD
AP
Y
AD2
AS2
1. A decrease in
aggregate demand . . .
2. . . . causes output to fall in the short run . . .
3. . . . but over
time, the short-run
aggregate-supply
curve shifts . . .
4. . . . and output returns
to its natural rate.
CP3
BP2
Y2
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