mankiw6e-chap_精品文档优质PPT.ppt

1、the physical and mental efforts of workersCHAPTER 3 National Incomeslide 4The production functiondenoted Y=F（K,L）shows how much output（Y）the economy can produce fromK units of capital and L units of labor reflects the economys level of technology exhibits constant returns to scaleCHAPTER 3 National

2、Incomeslide 5Returns to scale:A reviewInitially Y1 =F（K1,L1）Scale all inputs by the same factor z:K2 =zK1 and L2 =zL1 （e.g.,if z=1.25,then all inputs are increased by 25%）What happens to output,Y2=F（K2,L2）?If constant returns to scale,Y2=zY1 If increasing returns to scale,Y2 zY1 If decreasing return

3、s to scale,Y2 0CHAPTER 3 National Incomeslide 7Example 2decreasing returns to scale for any z 1CHAPTER 3 National Incomeslide 8Example 3increasing returns to scale for any z 1CHAPTER 3 National Incomeslide 9Now you tryDetermine whether constant,decreasing,or increasing returns to scale for each of t

4、hese production functions:（a）（b）CHAPTER 3 National Incomeslide 10Answer to part（a）constant returns to scale for any z 0CHAPTER 3 National Incomeslide 11Answer to part（b）constant returns to scale for any z 0CHAPTER 3 National Incomeslide 12Assumptions of the model1.Technology is fixed.2.The economys

5、supplies of capital and labor are fixed atCHAPTER 3 National Incomeslide 13Determining GDPOutput is determined by the fixed factor supplies and the fixed state of technology:CHAPTER 3 National Incomeslide 14The distribution of national incomedetermined by factor prices,the prices per unit that firms

6、 pay for the factors of production wage=price of Lrental rate=price of KCHAPTER 3 National Incomeslide 15Notation W =nominal wage R =nominal rental rate P =price of output W/P =real wage （measured in units of output）R/P=real rental rateCHAPTER 3 National Incomeslide 16How factor prices are determine

7、dFactor prices are determined by supply and demand in factor markets.Recall:Supply of each factor is fixed.What about demand?CHAPTER 3 National Incomeslide 17Demand for laborAssume markets are competitive:each firm takes W,R,and P as given.Basic idea:A firm hires each unit of labor if the cost does

8、not exceed the benefit.cost=real wagebenefit=marginal product of laborCHAPTER 3 National Incomeslide 18Marginal product of labor（MPL）definition:The extra output the firm can produce using an additional unit of labor（holding other inputs fixed）:MPL =F（K,L+1）F（K,L）CHAPTER 3 National Incomeslide 19Exer

9、cise:Compute&graph MPLa.Determine MPL at each value of L.b.Graph the production function.c.Graph the MPL curve with MPL on the vertical axis and L on the horizontal axis.LYMPL00n.a.110?219?3278434?540?645?749?852?954?1055?CHAPTER 3 National Incomeslide 20Answers:CHAPTER 3 National Incomeslide 21Yout

10、putMPL and the production functionLlabor1MPL1MPL1MPLAs more labor is added,MPL Slope of the production function equals MPLCHAPTER 3 National Incomeslide 22Diminishing marginal returnsAs a factor input is increased,its marginal product falls（other things equal）.Intuition:Suppose L while holding K fix

11、ed fewer machines per worker lower worker productivityCHAPTER 3 National Incomeslide 23Check your understanding:Which of these production functions have diminishing marginal returns to labor?CHAPTER 3 National Incomeslide 24Exercise（part 2）Suppose W/P=6.d.If L=3,should firm hire more or less labor?W

12、hy?e.If L=7,should firm hire more or less labor?LYMPL00n.a.110102199327843475406645574948523954210551CHAPTER 3 National Incomeslide 25MPL and the demand for laborEach firm hires labor up to the point where MPL=W/P.Units of outputUnits of labor,LMPL,Labor demandReal wageQuantity of labor demandedCHAP

13、TER 3 National Incomeslide 26The equilibrium real wageThe real wage adjusts to equate labor demand with supply.Units of outputUnits of labor,LMPL,Labor demandequilibrium real wageLabor supplyCHAPTER 3 National Incomeslide 27Determining the rental rateWe have just seen that MPL =W/P.The same logic shows that MPK =R/P:diminishing returns to capital:MPK as K The MPK curve is the firms demand curve for renting capital.Firms maximize profits by choosing K such that MPK=R/P.CHAPTER 3 National Incomeslide 28The equilibrium real ren