lecture 8: introduction to islm modelcoin.wne.uw.edu.pl/ggrotkowska/macro1_ang/macro1_0… · ·...
TRANSCRIPT
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Macroeconomics 1
Lecture 8: Introduction to ISLM Model
Dr Gabriela Grotkowska
Based on slides by Mankiw, Macoreconomcis, 5e
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The Big Picture
Keynesian
Cross
Theory of
Liquidity
Preference
IS
curve
LM
curve
IS-LM
model
Agg.
demand
curve
Agg.
supply
curve
Model of
Agg.
Demand
and Agg.
Supply
Explanation
of short-run
fluctuations
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Agenda for today
Deriving IS curve
Liquidity preference and money demand
Deriving LM curve
ISLM model
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4
Impact of interest rate on expenditures
r
r
G
C
NX
I
NX
G
I
C
In ISLM model we neglect weak impact of interest rates on private and public consumption (C, G). However we assume that interest rates havesignificant impact on investment and net exports
r
r
r
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The IS curve
def: a graph of all combinations of r
and Y that result in goods market
equilibrium,
i.e. actual expenditure (output)
= planned expenditure
The equation for the IS curve is:
𝒀 = 𝑪(𝒀 − 𝑻)+I(r)+ 𝑮 + 𝑵𝑿(𝒓)
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Y2Y1
Y2Y1
Deriving the IS curve
r I
Y
E
r
Y
E =C +I (r1 )+G
E =C +I (r2 )+G
r1
r2
E =Y
IS
I E
Y
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Why the IS curve is negatively sloped
A fall in the interest rate motivates
firms to increase investment
spending, which drives up total
planned spending (AE ).
To restore equilibrium in the goods
market, output (a.k.a. actual
expenditure, Y ) must increase.
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IS curve: algebraic approach
8
rnYmNXNX
GG
rbII
YcCC d
rnYmNXGrbIcYCY
NXGICAE
AEY
d
Equilibrium condition
AE
])1([ mtcYnrbrNXGIBcTcCY
])([( rnbAEY
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9
IS curve: algebraic approach vs graphical approach
])([( rnbAEY
Ynbnb
AEr
)(
1
nb
AE
)(
1
nbarctg
Y
r
A
B
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Interpretation of points above and below IS curve: disequilibrium
nb
AE
)(
1
nbarctg
Y
r
A
B
Ynbnb
AEr
)(
1
C
D
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11
Change in autonomous spending: illustration
Ynbnb
AEr
)(
1
nb
AE
1
nb
AE
2
r
Y
0IS 1IS
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12
Change in b and/or n: illustration
r
Y
0IS
1IS
Ynbnb
AEr
)(
1
nb
AE
1
nb
AE
0
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slide 13
The IS curve and the Loanable Funds model
S, I
r
I (r )r1
r2
r
YY1
r1
r2
(a) The L.F. model (b) The IS curve
Y2
S1S2
IS
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Fiscal Policy and the IS curve
We can use the IS-LM model to see how fiscal policy (G and T ) can affect aggregate demand and output.
Let’s start by using the Keynesian Cross to see how fiscal policy shifts the IS curve…
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Y2Y1
Y2Y1
Shifting the IS curve: G
At any value of
r, G E
Y
Y
E
r
Y
E =C +I (r1 )+G1
E =C +I (r1 )+G2
r1
E =Y
IS1
The horizontal
distance of the
IS shift equals
IS2
…so the IS curve
shifts to the right.
1
1 MPCY G
Y
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The Theory of Liquidity Preference
Due to John Maynard Keynes.
A simple theory in which the interest rate is determined by money supply and money demand.
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Money Supply
The supply of
real money
balances
is fixed:
s
M P M P
M/P
real money
balances
rinterest
rate
sM P
M P
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18
Demand for money in Keynes’ theory: stable or unstable?
J.M. Keynes (1936): liquidity preference concept
Demand for money = liquidity preference (how much of their assets people want to keep in a liquid form)
MD comes from the following motives:
transactions motive
precautionary motive
speculative motive
portfolio motive
DM1
DM 2
Demand = liquidity preference related to transitions (the level of output), stable part of MD
MD=kYp
Demand = liquidity preference related to speculations, unstable part of MD
MD=-hr
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Money Demand
Demand for
real money
balances:
M/P
real money
balances
rinterest
rate
sM P
M P
( )d
M P L r
L (r )
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Equilibrium
The interest
rate adjusts
to equate
the supply
and demand
for money:
M/P
real money
balances
rinterest
rate
sM P
M P
( )M P L r L (r )
r1
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How the Fed raises the interest rate
To increase r,
Fed reduces M
M/P
real money
balances
rinterest
rate
1M
P
L (r )
r1
r2
2M
P
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CASE STUDY
Volcker’s Monetary Tightening
Late 1970s: > 10%
Oct 1979: Fed Chairman Paul Volcker
announced that monetary policy
would aim to reduce inflation.
Aug 1979-April 1980:
Fed reduces M/P 8.0%
Jan 1983: = 3.7%
How do you think this policy change would affect interest rates?
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Volcker’s Monetary Tightening, cont.
i < 0i > 0
1/1983: i = 8.2%8/1979: i = 10.4%
4/1980: i = 15.8%
flexiblesticky
Quantity Theory, Fisher Effect
(Classical)
Liquidity Preference
(Keynesian)
prediction
actual outcome
The effects of a monetary tightening on nominal interest rates
prices
model
long runshort run
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The LM curve
Now let’s put Y back into the money
demand function:
( , )M P L r Y
The LM curve is a graph of all combinations of
r and Y that equate the supply and demand
for real money balances.
The equation for the LM curve is:
d
M P L r Y ( , )
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Deriving the LM curve
M/P
r
1M
P
L (r , Y1 )
r1
r2
r
YY1
r1
L (r , Y2 )
r2
Y2
LM
(a) The market for real money balances
(b) The LM curve
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26
LM curve
p
M
hY
h
kr
1
Y
r
Possible shifts:
• increase in M/p
Parallel shift to the right (down)
• increase in k
increase in the angle of inclination
• increase in h
decrease in the angle and shift down
LM
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27
Interpretation of points above and below LM curve: disequilibrium
LM
r
Y
C
D
B
A
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slide 28
How M shifts the LM curve
M/P
r
1M
P
L (r , Y1 )r1
r2
r
YY1
r1
r2
LM1
(a) The market for real money balances
(b) The LM curve
2M
P
LM2
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29
LM curve: examples of shifts
Increase in M/p
Increase in k rr
YY
LM
LM
LM1
LM1
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30
LM curve: examples of shifts
r
Y
LM
LM1
Increase in h
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The short-run equilibrium
The short-run equilibrium
is the combination of r
and Y that simultaneously
satisfies the equilibrium
conditions in the goods &
money markets: ( ) ( )Y C Y T I r G
Y
r
( , )M P L r Y
IS
LM
Equilibrium
interest
rate
Equilibrium
level of
income
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The Big Picture
Keynesian
Cross
Theory of
Liquidity
Preference
IS
curve
LM
curve
IS-LM
model
Agg.
demand
curve
Agg.
supply
curve
Model of
Agg.
Demand
and Agg.
Supply
Explanation
of short-run
fluctuations
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Lecture summary
1. Keynesian Cross
basic model of income determination
takes fiscal policy & investment as exogenous
fiscal policy has a multiplier effect on income.
2. IS curve
comes from Keynesian Cross when planned
investment depends negatively on interest rate
shows all combinations of r and Y
that equate planned expenditure with
actual expenditure on goods & services
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Lecture summary
3. Theory of Liquidity Preference
basic model of interest rate determination
takes money supply & price level as exogenous
an increase in the money supply lowers the interest
rate
4. LM curve
comes from Liquidity Preference Theory when money
demand depends positively on income
shows all combinations of r and Y that equate
demand for real money balances with supply
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Lecture summary
5. IS-LM model
Intersection of IS and LM curves shows
the unique point (Y, r ) that satisfies
equilibrium in both the goods and
money markets.
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Thank you and see next week:)