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Chapter Eleven1 A PowerPoint Tutorial to Accompany macroeconomics, 5th ed. N. Gregory Mankiw Mannig J. Simidian ® CHAPTER ELEVEN Aggregate Demand II

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Chapter Eleven2 Now that we’ve assembled the IS-LM model of aggregate demand, let’s apply it to three issues: 1) Causes of fluctuations in national income 2) How IS-LM fits into the model of aggregate supply and aggregate demand 3) The Great Depression Now that we’ve assembled the IS-LM model of aggregate demand, let’s apply it to three issues: 1) Causes of fluctuations in national income 2) How IS-LM fits into the model of aggregate supply and aggregate demand 3) The Great Depression

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Chapter Eleven3 IS-LM The intersection of the IS curve and the LM curve determines the level of national income. When one of these curves shifts, the short-run equilibrium of the economy changes, and national income fluctuates. Let’s examine how changes in policy and shocks to the economy can cause these curves to shift.

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Chapter Eleven4

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5 LM r Y IS A +G+G Consider an increase in government purchases. This will raise the level of income by G/(1- MPC) IS´ B The IS curve shifts to the right by G/(1- MPC) which raises income and the interest rate.

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Chapter Eleven6

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7 IS r Y LM A B +M+M Consider an increase in the money supply. The LM curve shifts downward and lowers the interest rate which raises income. Why? Because when the Fed increases the supply of money, people have more money than they want to hold at the prevailing interest rate. As a result, they start depositing this extra money in banks or use it to buy bonds. The interest rate r then falls until people are willing to hold all the extra money that the Fed has created; this brings the money market to a new equilibrium. The lower interest rate, in turn has ramifications for the goods market. A lower interest rate stimulates planned investment, which increases planned expenditure, production, and income Y.

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Chapter Eleven8 The IS-LM model shows that monetary policy influences income by changing the interest rate. This conclusion sheds light on our analysis of monetary policy in Chapter 9. In that chapter we showed that in the short run, when prices are sticky, an expansion in the money supply raises income. But, we didn’t discuss how a monetary expansion induces greater spending on goods and services--a process called the monetary transmission mechanism. The IS-LM model shows that an increase in the money supply lowers the interest rate, which stimulates investment and thereby expands the demand for goods and services.

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Chapter Eleven9

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10 You probably noticed from the IS and LM diagrams that r and Y were on the two axes. Now we’re going to bring a third variable, the price level (P) into the analysis. We can accomplish this by linking both two- dimensional graphs. r P Y Y IS LM(P 1 ) A A AD To derive AD, start at point A in the top graph. Now increase the price level from P 1 to P 2. An increase in P lowers the value of real money balances, and Y, shifting LM leftward to point B. The + P triggers a sequence of events that end with a - Y, the inverse relationship that defines the downward slope of AD. Notice that r increased. Since r increased, we know that investment will decrease as it just got more costly to take on various investment projects. This sets off a multiplier process since - I causes a – Y. The - Y triggers - C as we move up the IS curve. LM(P 2 ) B B P2P2 P1P1

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Chapter Eleven11 +G+G This translates into a rightward shift of the IS and AD curves. LM (P 2 ) Suppose there is a + G. In the short-run, we move along SRAS from point A to point B. But as the output market clears, in the long-run, the price level will increase from P 0 to P 2. This + P decreases the value of real money balances, which translates into a leftward shift of the LM curve. Finally, this leaves us at point C in both diagrams. r P Y Y IS LM (P 0 ) AD P0P0 AD´ IS´ SRAS A A B B P2P2 C C LRAS Y = C (Y-T) + I(r) + G M/ P = L (r, Y)

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Chapter Eleven12 Now it’s time to determine the effects on the variables in the economy. For the variables Y, P, and r, you can read the effects right off the diagrams. Remember that SR is the movement from A to B. +, because Y moved from Y* to Y´ 0, because prices are sticky in the SR. +, because a + Y leads to a rise in r as IS slides along the LM curve. +, because a + Y increases the level of consumption ( C=C( Y-T)). –, since r increased, the level of investment decreased. Y P r C I r P Y Y IS LM(P 0 ) AD P0P0 AD´ IS´ SRAS A A B B P2P2 C C LRAS * YY´ LM(P 2 )

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Chapter Eleven13 +, in order to eliminate the excess demand at P 0. 0, because rising P shifts LM to left, returning Y to Y* as required by long-run LRAS. +, reflecting the leftward shift in LM due to + P 0, since both Y and T are back to their initial levels (C=C(Y-T)) – –, since r has risen even more due to the + P. Y P r C I For the variables Y, P and r, you can read the effects right off the diagrams. Remember that LR is the movement from A to C. r P Y Y IS LM(P 0 ) AD P0P0 AD´ IS´ SRAS A A B B P2P2 C C LRAS * YY´ LM(P 2 )

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Chapter Eleven14 LM B AD´ B Notice that M \ was increased, thus increasing the value of the real money supply which translates into a rightward shift of the LM and AD curves. Suppose there is a + M. Look at the appropriate equation that captures the M term: In the short-run, we move along SRAS from point A to point B. But as the output market clears, in the long-run, the price level will increase from P 0 to P 2. This + P decreases the value of the real money supply which translates into a leftward shift of the LM curve. Finally, this leaves us at point C in both diagrams. C AD IS r P Y Y LM (P 0 ) P0P0 SRAS A A LRAS = C P2P2 M/ P = L (r, Y)

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Chapter Eleven15 Now it’s time to determine the effects on the variables in the economy. For the variables Y, P, and r, you can read the effects right off the diagrams. Remember that SR is the movement from A to B. +, because Y moved from Y* to Y´ 0, because prices are sticky in the SR. –, because a + Y leads to a decrease in r as LM slides along the IS curve. +, because a + Y increases the level of consumption ( C=C( Y-T)). +, since r increased, the level of investment decreased. Y P r C I LM B AD´ B C AD IS r P Y Y LM (P0) P 0 SRAS A A LRAS = C P 2 (P2) Y´ Y*Y*

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Chapter Eleven16 +, in order to eliminate the excess demand at P 0. 0, because rising P shifts LM to left, returning Y to Y* as required by LRAS. 0, reflecting the leftward shift in LM due to + P, restoring r to its original level. 0, since both Y and T are back to their initial levels (C=C(Y-T)). 0, since Y or r has not changed. Y P r C I For the variables Y, P and r, you can read the effects right off the diagrams. Remember that LR is the movement from A to C. Notice that the only LR impact of an increase in the money supply was an increase in the price level. LM B AD´ B C = C P 2 AD IS r P Y Y LM (P0) P 0 SRAS A A LRAS Y´ Y*Y*

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Chapter Eleven17

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Chapter Eleven18 LM(P 0 ) 1) + C causes the IS curve to shift right to IS‘. LRAS 2) This leads to a rightward shift in AD to AD’. Short Run: Move from A to B. Long Run: Market clears at P 0 to P 2 from B to C. 3) + P causes LM(P 0 ) to shift leftward to LM(P 2 ) due to the lowering of the real value of the money supply. r Y P Y IS AD IS' P0P0 AD' LRAS LM(P 2 ) P2P2 C C Y = C (Y-T) + I(r) + G IS-LM M/ P = L (r, Y)

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Chapter Eleven19 Short Run: Y+ P0 r+ C+ I- Long Run: SRAS r Y P Y IS AD IS' P 0 AD' LRAS LM(P 2 ) P 2 C C LM(P 0 )

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Chapter Eleven20 The spending hypothesis suggests that perhaps the cause of the decline may have been a contractionary shift of the IS curve. The money hypothesis attempts to explain the effects of the historical fall of the money supply of 25% from 1929 to 1933 during which time unemployment rose from 3.2% to 25.2.%. Some economists say that deflation worsened the Great Depression. They argue that the deflation may have turned what in 1931 was a typical economic downturn into an unprecedented period of high unemployment and depressed income. Because the falling money supply was possibly responsible for the falling price level, it could very well have been responsible for the severity of the depression. Let’s see how changes in the price level affect income in the IS-LM model.

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Chapter Eleven21 LM Y IS A IS´ B An expected deflation (a negative value of e ) raises the real interest rate for any given nominal interest rate, and this depresses investment spending. The reduction in investment shifts the IS curve downward. The level of income and the nominal interest rate (i) fall, but the real interest rate (r) rises. i2i2 r 1 = i 1 r2r2 interest rate, i

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Chapter Eleven22 Monetary transmission mechanism Pigou Effect Debt-deflation theory Monetary transmission mechanism Pigou Effect Debt-deflation theory

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