曼昆宏觀經(jīng)濟(jì)學(xué)練習(xí)題及答案

1、Homework 3 (suggested solution)Due date: Dec 151. Suppose that the following equations describe an economy (C, I, G, T, and Y are measured in billions of dollars and r is measured in percent; for example, r = 10 means r = 10 percent):C = 170 + 0.6(Y - T)T = 200I = 100 - 4rG = 350(M/P)d = L = 0.75Y 6

2、rMs/P = M/P = 735.a. Graph the IS and LM curve and show me the slopes and intercepts.slope of IS curve = 1/10; slope of LM curve = 1/8b. Calculate the equilibrium levels of real output Y, the interest rate r, planned investment I, and consumption C.r = 15 (percent); Y = 1,100; I = 40; C = 710c. At t

3、he equilibrium level of real output Y, calculate the value of the government budget surplus.-150d. Suppose that G increases by 36 to 386. Derive the new IS and LM equations and plot and draw these curves on the graph you drew for Part a.The LM equation remains unchanged. The new IS equation is Y = 1

4、,340 - 10r.e. What is the horizontal shift in the IS curve and/or the LM curve in Part d (i.e., if r remains constant, by how much does Y increase on each curve)?The shift in the IS curve is equal to 90. The LM curve does not shift.f. Refer to the IS and LM equations you derived in Part d. With Y on

5、 the left-hand side of the equations, calculate the new equilibrium levels of real output Y, the interest rate r, planned investment I, and consumption C.Y = 1,140; r = 20; I = 20; C = 734g. Instead of increasing G, suppose that the Fed sought to achieve the equilibrium level of real output Y in Par

6、t h through expansionary monetary policy alone. By how much would the Fed have to increase the money supply? 54h. Compare the equilibrium levels of consumption C, government spending G, and planned investment I in Parts f and g. Based on this comparison, why might some economists prefer expansionary

7、 fiscal policy while others prefer expansionary monetary policy?Government purchases are higher in Part f. Since taxes and output are the same as Parts f and g, consumption is also the same. Since the interest rate is lower in Part g, investment is higher. Advocates of expansionary fiscal policy may

8、 argue that the United States is badly in need of public spending in areas like education, defense, and infrastructure. Advocates of expansionary monetary policy, on the other hand, would tout its effect on investment, which might spur economic growth as the capital stock grows.2. a. In 2009, Presid

9、ent Obama increased government spending and cut net taxes. Draw the appropriate graphs to indicate what would happen to the IS, LM, aggregate demand, and short-run aggregate supply curves, and indicate any short-run changes in the equilibrium levels of r, I, C, G, Y, and P if the Fed had not changed

10、 any of its policies.An increase in G and cut in net taxes T shift the IS and AD curves to the right (or IS and AD curves shift upward). The SRAS and LM curves do not shift in the short run.The equilibrium levels of Y, r, and C all rise. The equilibrium level of I falls, and G and P do not change in

11、 the short run (given the horizontal SRAS curve of Chapter 9)b. During this period, the Fed actually pursued expansionary monetary policy and kept interest rates nearly constant. Redraw your diagrams from Part a and indicate what actually happened to the IS curve, LM curve, aggregate demand curve, s

12、hort-run aggregate supply curve, and the levels of r, I, C, G, Y, and P. How do they compare with the levels in Part a?The Federal Reserve increased the money supply at the same time as government spending rose and taxes fell. Consequently, both the IS and LM curves shifted to the right. This shifte

13、d the AD curve even farther to the right.The levels of Y and C rise by more in Part b than in Part a. The remaining variables, r, I, G, and P remain constant.3. The Fed is considering two alternative monetary policies: holding the money supply constant and letting the interest rate adjust, or adjust

14、ing the money supply to hold the interest rate constant.In the ISLM model, which policy will better stabilize output under the following conditions?a. All shocks to the economy arise from exogenous changes in the demand for goods and services.Figure 1125(A) shows what the ISLM model looks like for t

15、he case in which the Fed holds the money supply constant. Figure 1125(B) shows what the model looks like if the Fed adjusts the money supply to hold the interest rate constant; this policy makes the effective LM curve horizontal.If all shocks to the economy arise from exogenous changes in the demand

16、 for goods and services, this means that all shocks are to the IS curve. Suppose a shock causes the IS curve to shift from IS1 to IS2. Figures 1126(A) and (B) show what effect this has on output under the two policies. It is clear that output fluctuates less if the Fed follows a policy of keeping th

17、e money supply constant. Thus, if all shocks are to the IS curve, then the Fed should follow a policy of keeping the money supply constant.b. All shocks to the economy arise from exogenous changes in the demand for money.If all shocks in the economy arise from exogenous changes in the demand for mon

18、ey, this means that all shocks are to the LM curve. If the Fed follows a policy of adjusting the money supply to keep the interest rate constant, then the LM curve does not shift in response to these shocksthe Fed immediately adjusts the money supply to keep the money market in equilibrium. Figures 1127(A) and (B) show the effects of the two policies. It is clear that output fluctuates less if the Fed holds the interest rate constant, as in Figure 1127(B). If the Fed h