1     

By explicitly including the MP and IS curves in the aggregate demand and supply analysis, we can analyze the response of asset prices, in particular real interest rates and stock prices, to the macroeconomic shocks we discussed in the chapter. We start by using aggregate supply and demand analysis with the MP and IS curves to explain the impact of demand and supply shocks on real interest rates, inflation, and aggregate output. Then, using a standard formula for valuation of stocks, we use these results to see the impact of these shocks on stock prices.

Impact of Demand Shocks on Real Interest Rates, Inflation, and Output

Demand shocks are of two types, those that occur from shocks to monetary policy and those that occur from shocks to spending.

Monetary Policy ShocksSuppose the economy is initially at point 1 in all three panels of Figure 12A2.1, where inflation is at π1, aggregate output is at Y1 = Y P, and the real interest rate is at r1. Suppose also that the Federal Reserve decides to autonomously ease monetary policy by lowering real interest rates at any given inflation rate. As we can see in panel (a) of Figure 12A2.1, this monetary policy action results in a downward shift of the monetary policy curve from MP1 to MP2. This monetary policy shock does not cause the IS curve to change in panel (b), although it does lead to a movement along this IS curve. As we saw in Chapter 10, the aggregate demand curve in panel (c) shifts out to the right from AD1 to AD2, because the lower real interest rate at any given inflation rate leads to

Chapter 12 Appendix B

The Effects of Macroeconomic Shocks on Asset Prices

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2     chapter 12 appendix B

Figure 12A2.1

response to an Autonomous Monetary easingThe Fed’s decision to lower interest rates at any given inflation rate shifts the monetary policy curve from MP1 to MP2 in panel (a) and shifts the aggregate demand curve in panel (c) out to the right to AD2, because the lower real interest rate at any given inflation rate leads to higher consumption, invest-ment spending, and net exports. The economy moves to point 2 in all the panels, with both a higher rate of inflation at π2 and higher output at Y2, and as can be seen from the IS curve, the real interest rate falls to r2. The short-run aggregate supply curve will now shift up until it reaches AS3, and the economy moves to point 3, where aggre-gate output is now back at potential and infla-tion has risen to π3. The real interest rate is back at r1 because out-put is back at Y1 = Y P.

Inflation Rate, p

RealInterestRate, r

(a) MP Curve

p1 p3p2

r1

r2

1 3

MP1

MP2

(b) IS Curve

Aggregate Output, Y

(c) AD/AS Diagram

Aggregate Output, Y

InflationRate, p

2

Step 1. Autonomous monetaryeasing temporarily reducesreal interest rates…

RealInterestRate, r

Y1 Y2

r1

r2

1, 3

IS

2

YP = Y1

p3

p2

p1

AD2

Y2

3

AS3

AS1

LRAS

2

1

AD1

Step 2. which temporarilyraises aggregate outputin the IS diagram…

Step 4. but permanentlyraises inflation.

Step 3. and temporarilyraises output in theAD/AS diagram…

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the effects of MacroeconoMic shocks on asset prices     3     

higher investment spending and net exports, thereby increasing equilibrium output at each inflation rate. The rightward shift in the aggregate demand curve then moves the economy to point 2 in all the panels, with both a higher rate of inflation at π2 and higher output at Y2, and as we can see from the IS curve in panel (b), the real interest rate falls to r2.

As we saw in the chapter, because output is now above potential, the short-run aggregate supply curve in panel (c) will shift up until it reaches AS3. The economy moves to point 3, where aggregate output is now back at potential and inflation has risen to π3. From the IS curve in panel (b), we can see that the real interest rate is back at r1 because output is back at Y1 = Y P.

The conclusion from this exercise is that an autonomous monetary policy easing reduces real interest rates and raises aggregate output temporarily, but not perma-nently. On the other hand, the inflation rate does rise permanently.

This result formally illustrates a point we will discuss in Chapter 13, that monetary policy authorities can affect real interest rates in the short run, but they do not control real interest rates in the long run. Indeed, as we see in panel (b), the long-run real inter-est rate is determined by the IS curve, at which savings equals investment in goods market equilibrium, which is consistent with the analysis in Chapter 4.

Spending ShocksSpending shocks can occur either because of changes in fiscal policy (changes in taxes or government purchases) or because of autonomous changes in consumption expendi-ture, investment spending, or net exports. Let’s see what happens when there is a posi-tive spending shock, either because government purchases increase or because business optimism leads to an increase in investment. Because monetary policy is unchanged, the MP curve in panel (a) of Figure 12A2.2 does not shift. The IS and AD curves in panels (b) and (c), however, shift out to the right, as we learned in Chapters 9 and 10, because increased spending causes equilibrium output to increase at any given inflation and real interest rate. The economy moves to point 2 in panel (c), with both output and inflation higher at Y2 and π2. Because inflation is higher, we see from panels (a) and (b) that the real interest rate has risen to r2. Then, as we saw in the previous example, the aggregate supply curve shifts up to AS3, and the economy moves to point 3. Output returns to potential, but notice that because inflation rises to π3, the real interest rate rises even further to r3 in panels (a) and (b).

The conclusion from this analysis is that positive spending shocks lead to higher real interest rates in both the short and long run. Positive spending shocks lead to higher output in the short run, but not in the long run, and do lead to higher inflation in both the short run and long run.

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4     chapter 12 appendix B

Figure 12A2.2

response to a Positive Spending ShockA positive spending shock shifts the IS and AD curves to the right to IS2 in panel (b) and to AD2 in panel (c). The economy moves to point 2, with both output and inflation higher at Y2 and π2. Because infla-tion is higher, we see from panels (a) and (b) that the short-run real interest rate rises to r2. The short-run aggregate supply curve then shifts up to AS3, and the economy moves to point 3. Output returns to potential, but because inflation rises to π3, the real interest rate rises even further to r3.

Inflation Rate, p

RealInterestRate, r

(a) MP Curve

p1

(b) IS Curve

Aggregate Output, Y

(c) AD/AS Diagram

Aggregate Output, Y

InflationRate, p

Step 4. Short-run andlong-run inflation increase.

RealInterestRate, r

Y1 Y2

YP = Y1

p3

p2

p1

AD2

Y2

3

AS3

AS1

LRAS

2

1

AD1

Step 3. Short-run outputincreases, but long-runoutput remains unchanged.

r3

r2

r1

r3

r2

r1

32

1

MP

32

1

p2 p3

Step 2. Short-run andlong-run real interestrates increase.

Step 1. Positivespending shockshifts IS to right.

IS1

IS2

Step 2. andshifts AD to right.

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the effects of MacroeconoMic shocks on asset prices     5     

Impact of Supply Shocks on Real Interest Rates, Inflation, and Output

Now we look at the effects of temporary and permanent supply shocks.

Temporary Supply ShocksAs in the chapter, we examine a temporary negative supply shock resulting from a rise in oil prices in Figure 12A2.3. The supply shock leads to an upward shift in the aggre-gate supply curve from AS1 to AS2 in panel (c), but does not lead to a shift in the MP or IS curves in either panel (a) or (b). When the economy moves to point 2, where output has fallen to Y2 and inflation has risen to π2, we see that the real interest rate rises to r2 at point 2 on both the MP and IS curves in panels (a) and (b). Then, as we saw in the text, in the long run the aggregate supply curve will shift back down to AS1 and the economy will return to point 1 in all the panels, so inflation, output, and the real interest rate return to their initial levels.

The conclusion is the following: a temporary supply shock that raises prices will cause the real interest rate to rise in the short run, but not in the long run. Although the temporary supply shock causes inflation to rise and output to fall in the short run, it has no long-run impact on either of these variables.

Permanent Supply ShocksIn Figure 12A2.4, we look at a permanent negative supply shock. In this case, in panel (c), the long-run supply curve shifts leftward from LRAS1 to LRAS2, while the short-run aggregate supply curve shifts up from AS1 to AS2. However, again neither the MP or IS curves shift in panels (a) or (b). When the economy moves to point 2 in all three panels, inflation rises to π2, output falls to Y2, and the real interest rate rises to r2.

A permanent negative supply shock leads to higher real interest rates in both the short and the long run. It also results in lower output in both the long and the short run, and higher inflation in both the short and the long run.

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6     chapter 12 appendix B

Figure 12A2.3

response to a Temporary Negative Supply ShockThe temporary negative supply shock leads to an upward shift in the aggregate supply curve to AS2 in panel (c). When the economy moves to point 2, where output has fallen to Y2 and inflation has risen to π2, the interest rate rises to r2 at point 2 on both the MP and IS curves in panels (a) and (b). In the long run, the aggregate supply curve will shift back down to AS1 and the economy will return to point 1, where inflation, output, and the real interest rate return to their ini-tial levels.

Inflation Rate, p

RealInterestRate, r

(a) MP Curve

p2

r2

r1

2

MP

(b) IS Curve

Aggregate Output, Y

(c) AD/AS Diagram

Aggregate Output, Y

InflationRate, p

Step 3. increasing realinterest rates in the short run…

RealInterestRate, r

Y2 Y1

r2

r1

2

IS

1

Y2

p2

p1

AD1

YP = Y1

2

AS2

AS1

LRAS1

1

Step 4. and decreasingoutput in the short run.

Step 1. A temporarynegative supply shockshifts AS upward…

p1

1

Step 2. increasing inflation andlowering output in the short run…

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the effects of MacroeconoMic shocks on asset prices     7     

Figure 12A2.4

response to a Permanent Negative Supply ShockIn panel (c), the permanent negative supply shock shifts the long-run supply curve to the left to LRAS2, while the short-run aggregate supply curve shifts up to AS2. When the economy moves to point 2, inflation rises to π2, while output falls to Y2. The higher infla-tion rate is then asso-ciated with a higher real interest rate r2, as shown in panels (a) and (b).

Inflation Rate, p

RealInterestRate, r

(a) MP Curve

p2

r2

r1

2

MP

(b) IS Curve

Aggregate Output, Y

(c) AD/AS Diagram

Aggregate Output, Y

InflationRate, p

Step 3. increasing realinterest rates in the long run…

RealInterestRate, r

Y2 Y1

r2

r1

2

IS

1

YP2

p2

p1

AD1

YP1

2

AS2

AS1

LRAS2 LRAS1

1

Step 4. and decreasingoutput in the long run.

Step 1. A permanentnegative supply shockshifts LRAS leftwardand AS upward…

p1

1

Step 2. increasing inflationin the long run…

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8     chapter 12 appendix B

Impact of Shocks on the Stock MarketTo assess the impact of these shocks on the stock market, we use a valuation formula for stock prices known as the generalized dividend model. It says that the value of a share of stock should equal the present discounted value of future dividends. We write this model as follows:

P0 = a∞

t=1

Dt

11 + rs2 t (1)

where

P0 = the current price of the stock, where the zero subscript refers to time period zero, that is, the present

Dt = the dividend paid at time t

rs = the investor’s required return for the stock

Future dividends should be positively related to overall economic activity and thus to aggregate output, while the required rate of return on stocks that we use to discount the future dividends would move positively with the real interest rate. Armed with these facts, we can now use the results to see what happens to stock prices as a result of demand and supply shocks.

Monetary Policy ShocksWe saw in Figure 12A2.1 that an autonomous monetary policy easing lowers real inter-est rates and raises output in the short run. The lower real interest rates reduce the denominator and higher output raises the numerator in Equation 1, thereby raising stock prices. We get the following result: an autonomous monetary policy easing should raise stock prices.

Spending ShocksIn Figure 12A2.2, we saw that a positive spending shock leads to both higher output and real interest rates in the short run and higher real interest rates in the long run. Here the effects on stock prices are unclear. The higher output raises the numerator in Equation 1 and would raise stock prices, while higher real interest rates would increase the denominator and cause stock prices to fall. The effect of a positive spending shock on stock prices is ambiguous.

Temporary Supply ShocksIn Figure 12A2.3, we saw that a temporary negative supply shock causes output to fall in the short run and real interest rates to rise. The denominator in Equation 1 rises, while the numerator falls, both lowering stock prices. A temporary negative supply shock should cause stock prices to fall.

Permanent Supply ShocksA permanent negative supply shock causes output to fall in the short run, as we saw in Figure 12A2.4, and also causes output to decline in the long run. Furthermore, it results in a higher real interest rate both in the short and long run. The fall in the numerator

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the effects of MacroeconoMic shocks on asset prices     9     

and rise in the denominator of Equation 1 are thus likely to be much larger than was the case for the temporary supply shock, because the effects are long-lasting. A perma-nent negative supply shock therefore causes stock prices to fall even more than they would if the supply shock were temporary.

We see from the analysis in this appendix that macroeconomic shocks have an important impact on financial markets. But it works the other way, too: we will see in Chapter 15 that financial shocks can have major effects on the macroeconomy.

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rates, inflation, and aggregate output (dis-tinguish between temporary and permanent effects on these variables when appropriate).

4. Suppose that as a result of many years of investment in research and development of new technologies, an economy discovers a new way of producing energy using renew-able sources, like wind or solar power. Explain the effects of this technological breakthrough on real interest rates, inflation, and aggregate output (distinguish between temporary and permanent effects on these variables when appropriate).

5. For each of the following events, describe the effect on stock prices:

a) An autonomous monetary policy tightening

b) A decrease in government spending c) A temporary positive supply shock d) A permanent positive supply shock

1. Suppose the Federal Reserve announces that as conditions in the economy improve, it will undertake the necessary actions to promote economic recovery and price stability. This might require an autonomous tightening of monetary policy. What would be the effect of an autonomous tightening of monetary policy on real interest rates, output, and inflation in the United States? Explain your answer graphically.

2. In 2013, many European countries experi-enced difficult times. As a consequence, their imports from the United States decreased. Use a graph to explain the effect on inflation, inter-est rates, and aggregate output of a decrease in net exports in the United States.

3. Suppose a country gets most of its electricity from hydroelectric plants. Explain the effects of a rainy season that allows this country to produce cheaper electricity on real interest

REvIEw QuESTIOnS AnD PROBlEMS

no long-run impact on either of these variables. A permanent negative supply shock leads to higher real interest rates in both the short and the long run. It also results in lower output and higher inflation in both the short and the long run.

3. An autonomous monetary policy easing should raise stock prices. The effect of a posi-tive spending shock on stock prices is ambig-uous. A temporary negative supply shock should cause stock prices to fall. A permanent negative supply shock causes stock prices to fall even more than they would if the supply shock were temporary.

SuMMARy 1. An autonomous monetary policy easing leads

to a reduction in real interest rates and aggre-gate output temporarily, but not permanently. On the other hand, the inflation rate does rise permanently. Positive spending shocks lead to higher real interest rates in both the short and long run. Positive spending shocks lead to higher output in the short run, but not in the long run, and also lead to higher inflation in both the short and long run.

2. A temporary supply shock that raises prices will cause the real interest rate to rise in the short run, but not in the long run. Although the temporary supply shock causes inflation to rise and output to fall in the short run, it has

10     chapter 12 appendix B

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