1. ECON 671 – International Economics
Aggregate Demand & Supply
in the Open Economy

2. Short Run IS-LM-BP Model and Aggregate Demand

3. Open Economy SR Equilibrium: IS-LM-BP Model
IS-LM-BP Model described by 3 equations
(IS) Y = C (Y-T, W) + I(i) + G + NX(e, Y, YROW, W)
(LM) Ms/P= a(DR + IR)/P= f(Y, i, W, E(p))
(BP) BOP0 = NX(e, Y, YROW, W) + j(i, i*+ xa)
IS-LM-BP with Fixed Exchange Rate Regime:
Endogenous Variables: Y, i, M (BOP=DIR)
Exogenous Variables: G, T, DR, W, P, e
IS-LM-BP with Flexible Exchange Rate Regime:
Endogenous Variables: Y, i, e
Exogenous Variables: G, T, M (BOP=0), W, P

4. Effect of Domestic Price Level
Look at effects of rise in domestic prices, P.
Direct Effects
Rise in P lowers NX which shifts IS and BP Curves inwards.
Also lowers real money supply so LM Curve shifts back.
New internal equilibrium where new IS Curves intersect.
Y decreases at new intersection. This is new overall equilib.!!
This result occurs regardless of fixed or flexible EXR.
Aggregate Demand
AD Curve shows relationship between Domestic Price Level and Output for Open Economy.
Demonstrated this is downward-sloping regardless of EXR regime.

5. Increase in Domestic Prices
Interest
Rate
DP >0
BP(e1, P1)
BP(e0, P0)
IS(e1, P1)
DP >0
LM(Ms/P1)
DP >0
LM(Ms/P0) Y1 i0
IS(e0, P0) Y0
Income, Output

6. Open Economy AD Curve Begin at Price Level P1 with IS1, BP1, and LM*1.2.
LM2 2.
Begin at Price Level P1 with IS1, BP1, and LM*1.
1. Increase Price level to P2.
- All 3 curves shift inward.
2. Lower level of real GDP, Y2, at higher Price level P2.
3. AD Curve summarizes relationship of P and Y.
4. Anything that shifts IS, BP, or LM Curve (with Price level fixed) will shift AD Curve.
BP1
IS2 2. Y2 i2
LM1 i1
IS1
Price Y1 Y
Level Y2 P
AD(G,T,M,i*) 3. P2 1. P1 Y1 Y

7. Shifts in Aggregate Demand under Different EXR Regimes

8. AD Curve Shifts & Fixed EXR
Fiscal Policy
Shifts in IS Curve lead to shifts in AD Curve because Y changes.
Adjustments to equilibrium depend on degree of capital mobility.
Higher the degree of capital mobility, the more effective is fiscal policy.
When capital immobile, IR adjustment shifts LM in & increases i, Y fixed.
When capital mobile, IR adjustment shifts LM out & increases Y, i fixed.
Monetary Policy
Shifts in LM Curve do not affect AD curve because Y does not change.
Adjustment to equilibrium does not depend on degree of capital mobility.
Monetary policy is not effective in changing Y.
Change in Domestic Reserves brings changes in i & Y affecting FX market.
FX market disequilibrium, requires Central Bank to change Int’l Reserves by amount exactly offsetting original change in Domestic Reserves.
Exchange Rate Policy
Devaluation shifts both IS & BP curves, increasing Y, shifts AD curve out.
Central Bank intervention to achieve new fixed EXR brings about change.

9. AD Curve Shifts & Flexible EXR
Fiscal Policy
Shifts in IS affect AD Curve only to extent Y changes..
How much shift in IS changes Y depends on degree of capital mobility.
Higher the degree of capital mobility, the less effective is fiscal policy.
When capital immobile, EXR adjustment mostly shifts BP & increases Y.
When capital mobile, EXR adjustment mostly shifts IS & decreases Y.
Monetary Policy
Shifts in LM Curve lead to shifts in AD Curve because Y changes.
Shift in AD Curve does not depend on degree of capital mobility.
Monetary policy is very effective in changing Y & shifting AD Curve.
Most effective when capital perfectly mobile, keeps domestic i = i*.
Effect on interest rate uncertain in most cases, depends on relative shifts and slopes of IS and BP curves.

10. Short Run and Long Run Aggregate Supply

11. Short Run Aggregate Supply
Use standard model of SRAS. All variations of this model have a common theme.
(SRAS) Y = YLR + a(P- Pe) with a > 0
In SR, output deviates from LR level if actual price level deviates from expected price level.
This behavior arises from imperfection in a market.
Each of the four models focuses on slightly different rationale for imperfection.
These models imply a tradeoff between inflation and unemployment - but only a temporary one.
Called the Phillips Curve

12. Sticky Wage Model of SRAS
In labor market, nominal wage often sticky in SR.
Why? Unions, long term contracts, social norms.
If nominal wage, W, assumed fixed then;
Rise in Price level will reduce real wage, W/P.
Labor cheaper, firms hire more labor, increase output.
Higher Price level brings higher output = SRAS.
Nominal wage fixed by expected Price, Pe.
Bargain W = Target Real Wage x P e or W = w x Pe
Receive Actual real wage = W/P = w x (Pe/P)
If P > Pe actual real wage lower than target real wage.
Leads to SRAS: Y = YLR + a(P- Pe) a > 0

13. Worker Misperception Model
In labor market assume Nominal wage varies but workers confuse real & nominal wages.
Firms know Price level: Ld = Ld(W/P).
Workers do not know Price level: Ls = Ls(W/Pe)
rewrite Labor Supply as Ls = Ls(W/P x P/Pe)
Ls depends on real wage & worker misperceptions of P.
Unexpected increase in Price Level increases P/Pe.
Any real wage now associated with higher nom. wage.
Workers interpret as higher real wage. Ls shifts out.
Leads to SRAS: Y = YLR + a(P- Pe) a > 0

14. Imperfect Information Model
Focus on misperceptions of price in output market.
No-one in economy knows true average price level.
Supplier observes only price of single good they sell.
How much of price change in good due to inflation? How much from increase in relative demand?
If price change due to entirely inflation, real price unchanged
Supplier should not increase output., real profits same.
If price change from increased demand, real price increased.
Supplier should increase output because real profit higher.
Unexpected rise in price level for given expected price “fools” suppliers into increasing output.
Leads to SRAS: Y = YLR + a(P- Pe) a > 0

15. Misperception Model of SRAS
Y=YLR + a(P-Pe) 4.
4. Relationship between P and Y
Summarized by upward sloping SRAS.
Misperception Model of SRAS
Aggregate
Supply
1. Increase in Price level fools workers. P2 1.
3. Higher L results in higher output Y. Y2 3. L2 2.
Result is fall in Real wage, increase in L.
(W/P)2
2. LS shifts out given workers’ fixed Pe.
LS2 P1 Y1 Y Y
Labor Market
W/P
LS1
F(K0, L) Y1
(W/P)1
Ld(W/P)
Production L1 L L1 L

16. Short Run Aggregate Supply
1. SRAS upward sloping
Price Level
- depends on price expectations P
LRAS
2. LRAS vertical
Pe = P in LR equilib. P1
DPe
- increase in Pe shifts SRAS up. P2
3. Change in expected price
Y = YLR + a (P - Pe1) 1 a Y1
Income, Output, Y

17. SR vs. LR Effects in an Open Economy AD-AS Model

18. Shift in AD Curve: SR vs LR
1. AD Curve shifts out
- Price expectations fixed 1.
Price Level
LRAS P
YSR
2. In SR: Higher YSR and PSR
PSR 2.
3. DPe
- increase in Pe shifts SRAS up.
3. Change in expected price
SRAS2
P2LR 4.
4. In LR: back to YLR at
higher Price level.
SRAS1
P1LR
AD1
YLR
Income, Output, Y