宏观经济学课件13PPT推荐.ppt

1、macroeconomics fifth editionN.Gregory MankiwPowerPoint Slides by Ron Cronovichmacro 2002 Worth Publishers,all rights reservedCHAPTER THIRTEENAggregate SupplyCHAPTER 13CHAPTER 13 Aggregate Supply Aggregate SupplyLearning objectivesthree models of aggregate supply in which output depends positively on

2、 the price level in the short runthe short-run tradeoff between inflation and unemployment known as the Phillips curve1CHAPTER 13CHAPTER 13 Aggregate Supply Aggregate SupplyThree models of aggregate supply1.The sticky-wage model2.The imperfect-information model3.The sticky-price modelAll three model

3、s imply:#natural rate of outputa positive parameterthe expected price levelthe actual price levelagg.output2CHAPTER 13CHAPTER 13 Aggregate Supply Aggregate SupplyThe sticky-wage modelAssumes that firms and workers negotiate contracts and fix the nominal wage before they know what the price level wil

4、l turn out to be.The nominal wage,W,they set is the product of a target real wage,and the expected price level:#3CHAPTER 13CHAPTER 13 Aggregate Supply Aggregate SupplyThe sticky-wage modelIf it turns out thatthenunemployment and output are at their natural ratesReal wage is less than its target,so f

5、irms hire more workers and output rises above its natural rateReal wage exceeds its target,so firms hire fewer workers and output falls below its natural rate4CHAPTER 13CHAPTER 13 Aggregate Supply Aggregate SupplyThe sticky-wage modelImplies that the real wage should be counter-cyclical,it should mo

6、ve in the opposite direction as output over the course of business cycles:#In booms,when P typically rises,the real wage should fall.In recessions,when P typically falls,the real wage should rise.This prediction does not come true in the real world:#6CHAPTER 13CHAPTER 13 Aggregate Supply Aggregate S

7、upplyThe cyclical behavior of the real wagePercentage change in realwagePercentage change in real GDP1982197519931992196019961999199719981979197019801991197419901984200019721965-3-2-10123786544 3 2 1 0-1-2-3-4-57CHAPTER 13CHAPTER 13 Aggregate Supply Aggregate SupplyThe imperfect-information modelAss

8、umptions:#all wages and prices perfectly flexible,all markets cleareach supplier produces one good,consumes many goodseach supplier knows the nominal price of the good she produces,but does not know the overall price level8CHAPTER 13CHAPTER 13 Aggregate Supply Aggregate SupplyThe imperfect-informati

9、on modelSupply of each good depends on its relative price:#the nominal price of the good divided by the overall price level.Supplier doesnt know price level at the time she makes her production decision,so uses the expected price level,P e.Suppose P rises but P e does not.Then supplier thinks her re

10、lative price has risen,so she produces more.With many producers thinking this way,Y will rise whenever P rises above P e.9CHAPTER 13CHAPTER 13 Aggregate Supply Aggregate SupplyThe sticky-price modelReasons for sticky prices:#long-term contracts between firms and customersmenu costsfirms do not wish

11、to annoy customers with frequent price changesAssumption:#Firms set their own prices（e.g.as in monopolistic competition）10CHAPTER 13CHAPTER 13 Aggregate Supply Aggregate SupplyThe sticky-price modelAn individual firms desired price is where a 0.Suppose two types of firms:#firms with flexible prices,

12、set prices as abovefirms with sticky prices,must set their price before they know how P and Y will turn out:#11CHAPTER 13CHAPTER 13 Aggregate Supply Aggregate SupplyThe sticky-price modelAssume firms w/sticky prices expect that output will equal its natural rate.Then,To derive the aggregate supply c

13、urve,we first find an expression for the overall price level.Let s denote the fraction of firms with sticky prices.Then,we can write the overall price level as 12CHAPTER 13CHAPTER 13 Aggregate Supply Aggregate SupplyThe sticky-price modelSubtract（1s）P from both sides:#price set by flexible price fir

14、msprice set by sticky price firmsDivide both sides by s:#13CHAPTER 13CHAPTER 13 Aggregate Supply Aggregate SupplyThe sticky-price modelHigh P e High PIf firms expect high prices,then firms who must set prices in advance will set them high.Other firms respond by setting high prices.High Y High P When

15、 income is high,the demand for goods is high.Firms with flexible prices set high prices.The greater the fraction of flexible price firms,the smaller is s and the bigger is the effect of Y on P.14CHAPTER 13CHAPTER 13 Aggregate Supply Aggregate SupplyThe sticky-price modelFinally,derive AS equation by

16、 solving for Y:#15CHAPTER 13CHAPTER 13 Aggregate Supply Aggregate SupplyThe sticky-price modelIn contrast to the sticky-wage model,the sticky-price model implies a procyclical real wage:#Suppose aggregate output/income falls.Then,Firms see a fall in demand for their products.Firms with sticky prices reduce production,and hence reduce their demand for labor.The leftward shift in labor demand causes the real wage to fall.16CHAPTER 13CHAPTER 13 Aggregate Supply Aggregate SupplySummary&#implicationsEach of the thr