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1、1Chapter21Advanced Topics Item Item Item Etc.McGraw-Hill/Irwin Macroeconomics, 10e 2008 The McGraw-Hill Companies, Inc., All Rights Reserved.2IntroductionThis chapter offers advanced material presenting the revolution in macroeconomics that has developed over the last 30 yearsWe look at four theorie
2、s in this chapter:Rational expectationsThe random walk of GDPReal business cycle theoryNew Keynesian models of price stickinessThese models yield contrasting conclusions about the conduct of monetary policy, but they are alike in their emphasis on the importance of consistency between macroeconomic
3、and microeconomic theory.3Rational Expectations Equilibrium ModelsIn a rational expectations equilibrium model, markets clear and there is nothing systematic that monetary policy can do to affect output or unemploymentThe term “rational expectations equilibrium” identifies two key features of this a
4、pproachIt places weight on the role of expectations (rational ones)Economic agents do not know the future with certainty base their plans/decisions on their forecasts or expectations about the futureIf agents are rational, they will use all available information when forming those expectationsThe ra
5、tional expectations model insists on equilibriumMarkets clear immediately4Rational Expectations Equilibrium ModelsThe full neoclassical theory of AS asserts that:Unemployment is always at the natural rateOutput is always at the full-employment levelAny unemployment is purely frictionalNeither moneta
6、ry nor fiscal policy changes will have any systematic effect on outputThe rational expectations equilibrium approach offers a deviation from that model: Some people do not know the aggregate price level but do know the nominal wage or price at which they can buy or sell.5Rational Expectations Equili
7、brium ModelsAssume a simple AD schedule:(1) Assume a simple short run AS curve, including price expectations: (2) The AD and AS equations can be combined to solve for output (3) and prices (4) in terms of m and other variables Rewrite AD as p = m + v y, equating AD and AS, and solving for y:(3)6Rati
8、onal Expectations Equilibrium ModelsAssume a simple AD schedule:(1) Assume a simple short run AS curve, including price expectations: (2) The AD and AS equations can be combined to solve for output (3) and prices (4) in terms of m and other variables Plugging equation (3) into the rewritten AD sched
9、ule, and solve for p yields:(4) 7Rational Expectations Equilibrium ModelsTogether, equations (3) and (4) tell us the equilibrium output and prices in our model economyIf money supply rises 1 percent, output rises by 1/(1+) percent and prices rise by /(1+ ) percentIf m, v, and y* are known, given pri
10、ce expectations, predictions for y and p can be calculated using equations (3) and (4)Often the model generates values that are different from expectations the standard AS/AD model assumes that economic agents make predictions for the economy that are inconsistent with the predictions the model itse
11、lf makesThe Lucas Critique8The Perfect-Foresight ModelThe previous model can be altered to assume that economic agents are correct in their predictions, or p = peEconomic decision makers use equation (4) to predict prices and compute pe:(5)Collecting terms containing pe, we can rearrange (5) to give
12、 the perfect foresight forecast and solution for the price level and the corresponding solution for output: (6)(7)9The Perfect-Foresight ModelThe perfect-foresight predictions in equations (6) and (7) are quite different from the original AS/AD predictions embodied in equations (3) and (4)The latter
13、 assume exogenously given price expectationsThe former assume that price expectations are formed endogenously, and that expectation formation is consistent with the predictions of the modelThese differences have implications for the effectiveness of monetary policyUnder a perfect foresight model:A 1
14、% increase in the money supply leads to exactly a 1% increase in the price level A 1% increase in the money supply leads to NO increase in output 10A Rational Expectations ModelA rational expectations model assumes that:Agents make the best use of whatever information is available to themExpectation
15、s are formed in a manner consistent with the way the economy actually operatesSimilar to a perfect foresight model in which some of the key variables are uncertainSuppose before money supply is known, economic decision makers expect the money supply to equal meIf the money supply turns out to be m, the difference between agents expectations and the actual money supply is 11A Rational Expectations ModelThe monetary policy multiplier with respect to anticipated money, me, is zero, just as in
