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# Exercise-Macroeconomics2012

By Ray Alexander,2014-07-08 10:42
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Exercise-Macroeconomics20122012

Exercise

1 Here we investigate an economy without foreign trade. Suppose the consumption

CYD；;1000.6I50function is given by , while investment is given by . In

G250addition, the government purchase is given by , and tax revenue of the

T100government equals to .

YYD and disposable income in this case? a) What is the equilibrium level of income

b) Calculate the amount of public saving and private saving in equilibrium.

c) What is the value of multiplier?

Y900d) If , for some reason, output is at the level of 900 (), what will the level of unplanned

change in inventories?

Ie) If rises to 100, what will ht effect be on the equilibrium income?

CYD；;1000.8f) Now suppose the consumption behavior above changes so that , while the

other variables remain the same as above. Is the new equilibrium level of income higher or

lower than it was in problem 1a) ? Calculate the new equilibrium level to verify this.

g) In the case of problem 1f), if investment increases to 100, does this change in investment

Yspending have more or less of an effect on than it did in problem 1e)? Why?

a/ Y=C+I+G=100+0.6YD+50+250=400+0.6YD

YD=PI-T+Tran Pay

PI=NI-NAP-T-TSI+Tran Pay+Div

Y=C+S+T=C+I+T

净税收是政府税收减转移支付后的余额

YD= Y-T=Y-100 Y=YD+100

作出y=0.6x+400y=x+100 的图象如下

YD与Y的关系

980

960

940

920

900y=0.6x+400Y880y=+100860

840

820

800

780

700750800850900

YD

YYD其交点为！750,850，(即the equilibrium level of income and disposable income is

Y=850,YD=750

b/ S私人=Y-C-T=850-100-0.6*750-100=200

S公共=T-G=100-250= - 150

S= S私人+ S公共=I=50

c/MPC=?C/?YD=0.6

multiplier=1/(1-MPC)=2.5

d/计划外的存货变化=real GDPY-计划总支出！AE=900-C+I+G=50?

e/ Y=C+I+G=100+0.6Y-T+I+G

Y=250+2.5I+2.5G-1.5T I上升(Y也上升

而由于YD=Y-T(故Y上升时YD也跟着上升(且上升的幅度相同(故图像上升(；；；；

f/ Higher

Y=C+I+G=100+0.8YD+50+250=400+0.8YD

YD= Y-T=Y-100 Y=YD+100

1500,1600

g/|；；；；

2 Doing the exercise of Problem 4 on Page 777778 at the end of chapter 24 in our

textbook Macroeconomics

3 Draw a basic aggregate demand and aggregate supply graph (with LRAS constant) showing the economy in long-run equilibrium

a) Now assume that the government reduces the income tax. Show the resulting short-run

equilibrium on your diagram. Explain how the economy adjusts back to long-run equilibrium.

realGDP增加

b) Now assume that now there is an unexpected decrease in the price of gasoline. Show the

effects in the short-run and in the long-run. Explain how the economy adjusts back to the

long-run equilibrium. SUPPLY SHOCK

4 Doing the exercise of Problem 18 on Page 780 at the end of chapter 24 in our textbook Macroeconomics

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