Economics development and growth of data

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N. G R E G O R Y M A N K I W
PowerPoint® Slides
by Ron Cronovich
Aggregate Demand and Aggregate
Supply
33
ECONOMICS
P R I N C I P L E S O F
F O U R T H E D I T I O N

1
CHAPTER 33 AGGREGATE DEMAND AND AGGREGATE SUPPLY
Introduction
 Over the long run, real GDP grows about
3% per year on average.
 In the short run, GDP fluctuates around its trend.
• recessions: periods of falling real incomes
and rising unemployment
• depressions: severe recessions (very rare)
 Short-run economic fluctuations are often called
business cycles.

Three Facts About Economic Fluctuations
FACT 1: Economic fluctuations are
irregular and unpredictable.
FACT 2: Most macroeconomic
quantities fluctuate together.
FACT 3: As output falls,
unemployment rises.

3
Introduction, continued
 Explaining these fluctuations is difficult, and the
theory of economic fluctuations is controversial.
 Most economists use the model of
aggregate demand and aggregate supply
to study fluctuations.
 This model differs from the classical economic
theories economists use to explain the long run.

4
Classical Economics—A Recap
 The previous chapters are based on the ideas of
classical economics, especially:
 The Classical Dichotomy, the separation of
variables into two groups:
• real – quantities, relative prices
• nominal – measured in terms of money
 The neutrality of money:
Changes in the money supply affect nominal but
not real variables.

5
Classical Economics—A Recap
 Most economists believe classical theory
describes the world in the long run,
but not the short run.
 In the short run, changes in nominal variables
(like the money supply or P ) can affect
real variables (like Y or the u-rate).
 To study the short run, we use a new model.

6
The Model of Aggregate Demand and
Aggregate Supply
P
Y
AD
SRAS
P1
Y1
The price
level
Real GDP, the
quantity of output
The model
determines the
eq’m price level
and the eq’m
level of output
(real GDP).
“Aggregate
Demand”
“Short-Run
Aggregate
Supply”

7
The Aggregate-Demand (AD) Curve
The AD curve
shows the
quantity of
all g&s
demanded
in the economy
at any given
price level.
P
Y
AD
P1
Y1
P2
Y2

8
Why the AD Curve Slopes Downward
Y = C + I + G + NX
C, I, G, NX are
the components
of agg. demand.
Assume G fixed
by govt policy.
To understand
the slope of AD,
must determine
how a change in P
affects C, I, and NX.
P
Y
AD
P1
Y1
P2
Y2 Y1

9
The Wealth Effect (P and C )
 Suppose P rises.
 The dollars people hold buy fewer g&s,
so real wealth is lower.
 People feel poorer, so they spend less.
 Thus, an increase in P causes a fall in C
…which means a smaller quantity of g&s
demanded.

10
The Interest-Rate Effect (P and I )
 Buying g&s requires more dollars.
 To get these dollars, people sell some of their bonds
or other assets, which drives up interest rates.
…which increases the cost of borrowing to fund
investment projects.
 Thus, an increase in P causes a decrease in I
…which means a smaller quantity of g&s demanded.

The Exchange-Rate Effect (P and NX )
 Interest rates go up (the interest-rate effect).
 U.S. bonds more attractive relative to foreign bonds.
 Foreign investors purchase more U.S. bonds,
but first must convert their currency into $
…which appreciates the U.S. exchange rate.
 Makes U.S. exports more expensive to people
abroad, imports cheaper to U.S. residents.
 Thus, an increase in P causes a decrease in NX
…which means a smaller quantity of g&s
demanded.
11

12
The Slope of the AD Curve: Summary
An increase in P
reduces the quantity
of g&s demanded
because:
P
Y
AD
P1
Y1
• the wealth effect
(C falls)
P2
Y2
• the interest-rate
effect (I falls)
• the exchange-rate
effect (NX falls)

13
Why the AD Curve Might Shift
Any event that changes
C, I, G, or NX
– except a change in P –
will shift the AD curve.
Example:
A stock market boom
makes households feel
wealthier, C rises,
the AD curve shifts right.
P
Y
AD1
AD2
Y2
P1
Y1

14
The Aggregate-Supply (AS) Curves
The AS curve shows
the total quantity of
g&s firms produce
and sell at any given
price level.
P
Y
SRAS
LRAS
In the short run,
AS is
upward-sloping.
In the long run,
AS is vertical.

15
The Long-Run Aggregate-Supply Curve (LRAS)
The natural rate of
output (YN) is the
amount of output
the economy produces
when unemployment
is at its natural rate.
YN is also called
potential output
or
full-employment
output.
P
Y
LRAS
YN

16
Why LRAS Is Vertical
YN depends on the
economy’s stocks of
labor, capital, and
natural resources,
and on the level of
technology.
An increase in P
P
Y
LRAS
P1
does not affect
any of these,
so it does not
affect YN.
(Classical dichotomy)
P2
YN

17
Why the LRAS Curve Might Shift
Any event that
changes any of the
determinants of YN
will shift LRAS.
Example:
Immigration
increases L,
causing YN to rise.
P
Y
LRAS1
YN
LRAS2
YN
’

18
LRAS1980
Using AD & AS to Depict LR Growth and
Inflation
Over the long run,
tech. progress shifts
LRAS to the right
P
Y
AD1990
LRAS1990
AD1980
Y1990
and growth in the
money supply shifts
AD to the right.
Y1980
AD2000
LRAS2000
Y2000
P1980
Result:
ongoing inflation
and growth in
output.
P1990
P2000

19
Short Run Aggregate Supply (SRAS)
The SRAS curve
is upward sloping:
Over the period
of 1-2 years,
an increase in P
P
Y
SRAS
causes an
increase in the
quantity of g & s
supplied.
Y2
P1
Y1
P2

20
Why the Slope of SRAS Matters
If AS is vertical,
fluctuations in AD
do not cause
fluctuations in output
or employment.
P
Y
AD1
SRAS
LRAS
ADhi
ADlo
Y1
If AS slopes up,
then shifts in AD
do affect output
and employment.
Plo
Ylo
Phi
Yhi
Phi
Plo

21
Three Theories of SRAS
In each,
• some type of market imperfection
• result:
Output deviates from its natural rate
when the actual price level deviates
from the price level people expected.

22
Three Theories of SRAS
P
Y
SRAS
YN
When P > PE
Y > YN
When P < PE
Y < YN
PE
the expected
price level

23
1. The Sticky-Wage Theory
 Imperfection:
Nominal wages are sticky in the short run,
they adjust sluggishly.
• Due to labor contracts, social norms.
 Firms and workers set the nominal wage in
advance based on PE, the price level they
expect to prevail.

24
1. The Sticky-Wage Theory
 If P > PE,
revenue is higher, but labor cost is not.
Production is more profitable,
so firms increase output and employment.
 Hence, higher P causes higher Y,
so the SRAS curve slopes upward.

25
2. The Sticky-Price Theory
 Imperfection:
Many prices are sticky in the short run.
• Due to menu costs, the costs of adjusting
prices.
• Examples: cost of printing new menus,
the time required to change price tags.
 Firms set sticky prices in advance based
on PE.

26
2. The Sticky-Price Theory
 Suppose the Fed increases the money supply
unexpectedly. In the long run, P will rise.
 In the short run, firms without menu costs can
raise their prices immediately.
 Firms with menu costs wait to raise prices.
Meantime, their prices are relatively low,
which increases demand for their products,
so they increase output and employment.
 Hence, higher P is associated with higher Y,
so the SRAS curve slopes upward.

27
3. The Misperceptions Theory
 Imperfection:
Firms may confuse changes in P with changes
in the relative price of the products they sell.
 If P rises above PE, a firm sees its price rise
before realizing all prices are rising.
The firm may believe its relative price is rising,
and may increase output and employment.
 So, an increase in P can cause an increase in Y,
making the SRAS curve upward-sloping.

28
What the 3 Theories Have in Common:
Each of the 3 theories implies Y deviates from YN
when P deviates from PE.
Y = YN + a(P – PE)
Output
Natural rate
of output
(long-run)
a > 0,
measures
how much Y
responds to
unexpected
changes in P
Actual
price level
Expected
price level

29
SRAS and LRAS
 The imperfections in these theories are
temporary. Over time,
• sticky wages and prices become flexible
• misperceptions are corrected
 In the LR,
• PE = P
• AS curve is vertical

30
LRAS
SRAS
and LRAS
P
Y
SRAS
PE
Y = YN + a(P – PE)
YN
In the long run,
PE = P
and
Y = YN.

31
The Long-Run Equilibrium
In the long-run
equilibrium,
PE = P,
Y = YN ,
and unemployment
is at its natural rate.
P
Y
AD
SRAS
PE
LRAS
YN

32
Economic Fluctuations
 Caused by events that shift the AD and/or
AS curves.
 Four steps to analyzing economic fluctuations:
1. Determine whether the event shifts AD or AS.
2. Determine whether curve shifts left or right.
3. Use AD-AS diagram to see how the shift
changes Y and P in the short run.
4. Use AD-AS diagram to see how economy
moves from new SR eq’m to new LR eq’m.

PowerPoint® Slides
by Ron Cronovich
The Influence of Monetary and
Fiscal Policy on Aggregate Demand
34
ECONOMICS

1
CHAPTER 34 THE INFLUENCE OF MONETARY AND FISCAL POLICY
Aggregate Demand
 Recall, the AD curve slopes downward for three
reasons:
• the wealth effect
• the interest-rate effect
• the exchange-rate effect
 Next: a supply-demand model that helps
explain the interest-rate effect and how
monetary policy affects aggregate demand.
the most important
of these effects for
the U.S. economy

2
The Theory of Liquidity Preference
 A simple theory of the interest rate (denoted r)
 r adjusts to balance supply and demand
for money
 Money supply: assume fixed by central bank,
does not depend on interest rate

3
The Theory of Liquidity Preference
 Money demand reflects how much wealth
people want to hold in liquid form.
 For simplicity, suppose household wealth
includes only two assets:
• Money – liquid but pays no interest
• Bonds – pay interest but not as liquid
 A household’s “money demand” reflects its
preference for liquidity.
 The variables that influence money demand:
Y, r, and P.

4
Money Demand
 Suppose real income (Y) rises. Other things
equal, what happens to money demand?
 If Y rises:
• Households want to buy more g&s,
so they need more money.
• To get this money, they attempt to sell some of
their bonds.
 I.e., an increase in Y causes
an increase in money demand, other things equal.

5
How r Is Determined
MS curve is vertical:
Changes in r do not
affect MS, which is
fixed by the Fed.
MD curve is
downward sloping:
a fall in r increases
money demand.
M
Interest
rate MS
MD1
r1
Quantity fixed
by the Fed
Eq’m
interest
rate

6
How the Interest-Rate Effect Works
Y
P
M
Interest
rate
AD
MS
MD1
MD2
P2
P1
Y1 Y2
r2
r1
A fall in P reduces money demand, which lowers r.
A fall in r increases I and the quantity of g&s demanded.

7
Monetary Policy and Aggregate Demand
 To achieve macroeconomic goals, the Fed can
use monetary policy to shift the AD curve.
 The Fed’s policy instrument is the money supply.
 The news often reports that the Fed targets the
interest rate.
• more precisely, the federal funds rate – which
banks charge each other on short-term loans
 To change the interest rate and shift the AD curve,
the Fed conducts open market operations
to change the money supply.

8
The Effects of Reducing the Money Supply
Y
P
M
Interest
rate
AD1
MS1
MD
P1
Y1
r1
MS2
r2
AD2
Y2
The Fed can raise r by reducing the money supply.
An increase in r reduces the quantity of g&s demanded.

9
Fiscal Policy and Aggregate Demand
 Fiscal policy: the setting of the level of govt
spending and taxation by govt policymakers
 Expansionary fiscal policy
• an increase in G and/or decrease in T
• shifts AD right
 Contractionary fiscal policy
• a decrease in G and/or increase in T
• shifts AD left
 Fiscal policy has two effects on AD.

10
The Multiplier Effect
 If the govt buys $20b of planes from Boeing,
Boeing’s revenue increases by $20b.
 This is distributed to Boeing’s workers (as wages)
and owners (as profits or stock dividends).
 These people are also consumers, and will spend
a portion of the extra income.
 This extra consumption causes further increases
in aggregate demand.
Multiplier effect: the additional shifts in AD
that result when fiscal policy increases income
and thereby increases consumer spending

11
The Multiplier Effect
A $20b increase in G
initially shifts AD
to the right by $20b.
The increase in Y
causes C to rise,
which shifts AD
further to the right.
Y
P
AD1
P1
AD2
AD3
Y1 Y3
Y2
$20 billion

12
Marginal Propensity to Consume
 How big is the multiplier effect?
It depends on how much consumers respond to
increases in income.
 Marginal propensity to consume (MPC):
the fraction of extra income that households
consume rather than save
 E.g., if MPC = 0.8 and income rises $100,
C rises $80.

13
The Crowding-Out Effect
 Fiscal policy has another effect on AD
that works in the opposite direction.
 A fiscal expansion shifts AD to the right,
but also raises r,
which reduces investment and, thus,
reduces the net increase in agg demand.
 So, the size of the AD shift may be smaller than
the initial fiscal expansion.
 This is called the crowding-out effect.

14
How the Crowding-Out Effect Works
Y
P
M
Interest
rate
AD1
MS
MD2
MD1
P1
r1
r2
A $20b increase in G initially shifts AD right by $20b
But higher Y increases MD and r, which reduces AD.
AD3
AD2
Y1 Y2
$20 billion
Y3

15
Automatic Stabilizers
 Automatic stabilizers:
changes in fiscal policy that stimulate
agg demand when economy goes into recession,
without policymakers having to take any
deliberate action

16
Automatic Stabilizers: Examples
 The tax system
• Taxes are tied to economic activity.
When economy goes into recession,
taxes fall automatically.
• This stimulates agg demand and reduces the
magnitude of fluctuations.

17
Automatic Stabilizers: Examples
 Govt spending
• In a recession, incomes fall and
unemployment rises.
• More people apply for public assistance
(e.g., unemployment insurance, welfare).
• Govt outlays on these programs automatically
increase, which stimulates agg demand and
reduces the magnitude of fluctuations.

PowerPoint® Slides
by Ron Cronovich
The Short-Run Trade-off Between
Inflation and Unemployment
35
ECONOMICS

1
CHAPTER 35 THE SHORT-RUN TRADE-OFF
Introduction
 In the long run, inflation & unemployment are
unrelated:
• The inflation rate depends mainly on growth in
the money supply.
• Unemployment (the “natural rate”) depends on
the minimum wage, the market power of unions,
efficiency wages, and the process of job search.
 In the short run,
society faces a trade-off between
inflation and unemployment.

2
The Phillips Curve
 Phillips curve: shows the short-run trade-off
between inflation and unemployment

3
Deriving the Phillips Curve
 Suppose P = 100 this year.
 The following graphs show two possible
outcomes for next year:
A. Agg demand low,
small increase in P (i.e., low inflation),
low output, high unemployment.
B. Agg demand high,
big increase in P (i.e., high inflation),
high output, low unemployment.

4
Deriving the Phillips Curve
u-rate
inflation
PC
A. Low agg demand, low inflation, high u-rate
B. High agg demand, high inflation, low u-rate
Y
P
SRAS
AD1
AD2
Y1
103
A
105
Y2
B
6%
3% A
4%
5%
B

5
The Phillips Curve: A Policy Menu?
 Since fiscal and mon policy affect agg demand,
the PC appeared to offer policymakers a menu
of choices:
• low unemployment with high inflation
• low inflation with high unemployment
• anything in between
 1960s: U.S. data supported the Phillips curve.
Many believed the PC was stable and reliable.

6
The Vertical Long-Run Phillips Curve
 1968: Milton Friedman and Edmund Phelps
argued that the tradeoff was temporary.
 Natural-rate hypothesis: the claim that
unemployment eventually returns to its normal or
“natural” rate, regardless of the inflation rate
 Based on the classical dichotomy and the
vertical LRAS curve.

7
The Vertical Long-Run Phillips Curve
u-rate
inflation
In the long run, faster money growth only causes
faster inflation.
Y
P
LRAS
AD1
AD2
natural rate
of output
natural rate of
unemployment
P1
P2
LRPC
low
infla-
tion
high
infla-
tion

8
The Phillips Curve Equation
Short run
Fed can reduce u-rate below the natural u-rate
by making inflation greater than expected.
Long run
Expectations catch up to reality,
u-rate goes back to natural u-rate whether inflation
is high or low.
Unemp.
rate
Natural
rate of
unemp.
= – a Actual
inflation
Expected
inflation
–

9
How Expected Inflation Shifts the PC
Initially, expected &
actual inflation = 3%,
unemployment =
natural rate (6%).
Fed makes inflation
2% higher than expected,
u-rate falls to 4%.
In the long run,
expected inflation
increases to 5%,
PC shifts upward,
unemployment returns to
its natural rate.
u-rate
inflation
PC1
LRPC
6%
3%
PC2
4%
5%
A
B C

10
Another PC Shifter: Supply Shocks
 Supply shock:
an event that directly alters firms’ costs and
prices, shifting the AS and PC curves
 Example: large increase in oil prices

11
The Cost of Reducing Inflation
 Disinflation: a reduction in the inflation rate
 To reduce inflation,
Fed must slow the rate of money growth,
which reduces agg demand.
 Short run: output falls and unemployment rises.
 Long run: output & unemployment return to
their natural rates.

12
The Cost of Reducing Inflation
 Disinflation requires enduring a period of
high unemployment and low output.
 Sacrifice ratio: the number of percentage points
of annual output lost in the process of reducing
inflation by 1 percentage point
 Typical estimate of the sacrifice ratio: 5
• Reducing inflation rate 1% requires a sacrifice
of 5% of a year’s output.
 This cost can be spread over time. Example:
To reduce inflation by 6%, can either
• sacrifice 30% of GDP for one year
• sacrifice 10% of GDP for three years

13
Rational Expectations, Costless Disinflation?
 Rational expectations: a theory according to
which people optimally use all the information
they have, including info about govt policies,
when forecasting the future
 Early proponents:
Robert Lucas, Thomas Sargent, Robert Barro
 Implied that disinflation could be much less
costly…

14
The Volcker Disinflation
Fed Chairman Paul Volcker
• appointed in late 1979 under high inflation &
unemployment
• changed Fed policy to disinflation
1981-1984:
• Fiscal policy was expansionary,
so Fed policy needed to be very contractionary
to reduce inflation.
• Success: Inflation fell from 10% to 4%,
but at the cost of high unemployment…

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