中级宏观经济学Ch3国民收入.ppt

slide 0,第三章 国民收入：源于何处，去向何方,宏观经济学（第6版）,slide 1,在这一章，你将会学到：,什么决定了经济的总产出（或总收入）生产要素的价格是如何决定的总收入是如何分配的什么决定了对商品与服务的需求商品市场的均衡是如何实现的,slide 2,模型概要,封闭经济，市场出清供给方市场因素(供给，需求，价格)决定产出或收入需求方决定 C,I,G。均衡商品市场可借贷的资本市场,slide 3,生产要素,K=资本，用于生产的工具，机器，厂房等等L=劳动，包括体力和脑力劳动者,slide 4,生产函数,可表示为：Y=F(K,L)表明经济由K单位资本和L单位劳动能够有多少单位的产出（Y）反映了经济技术水平。表明规模报酬不变。,slide 5,规模报酬：复习,设最初生产函数为：Y1=F(K1,L1)假如所有的投入要素都扩大（减少）Z倍：K2=zK1 and L2=zL1(如果 z=1.25，那么，所有的投入都增长 25%)这时，产出会发生什么变化，Y2=F(K2,L2)?如果规模报酬不变，则Y2=zY1 如果规模报酬递增，则Y2 zY1 如果规模报酬递减，则Y2 zY1,slide 6,练习：决定下列函数的规模报酬,判断下列生产函数是规模报酬不变、递增还是递减？,slide 7,模型的假设前提,不考虑技术进步因素。资本与劳动的供给固定不变，即：,slide 8,GDP 的决定,产出是指在供给要素不变、技术水平不变的条件下的产出：,slide 9,国民收入的分配,由要素价格及生产要素的单位价格决定工资是劳动的价格租金率（利率）是资本的价格,slide 10,符号说明：,W=名义工资 R=名义租金率 P=产出的价格 W/P=实际工资(用于衡量单位产出)R/P=实际租金率,slide 11,要素价格是如何决定的,要素价格是由市场的供给与需求因素决定的。回顾：每种要素的供给是固定的需求的情况怎么样?,slide 12,The distribution of national income is determined by factor prices.Factor prices are the amounts paid to the factors of productionthewages workers earn and the rent the owners of capital collect.Because we have assumed a fixed amount of capital and labor,the factor supply curve is a vertical line.The next slide will illustrate.,Recall that the total output of an economy equals total income.Because the factors of production and the production functiontogether determine the total output of goods and services,they alsodetermine national income.,How is National Income Distributed to the Factors of Production?,slide 13,The price paid to any factor of production depends on the supply anddemand for that factors services.Because we have assumed thatthe supply is fixed,the supply curve is vertical.The demand curveis downward sloping.The intersection of supply and demanddetermines the equilibrium factor price.,FACTOR PRICES,slide 14,To make a product,the firm needs two factors of production,capital and labor.Lets represent the firms technology by the usual production function:Y=F(K,L)The firm sells its output at price P,hires workers at a wage W,and rents capital at a rate R.,Capital,Labor,slide 15,slide 16,The Firms Demand for Factors,We know that the firm will hire labor and rent capital in the quantities that maximize profit.But what are those maximizing quantities?To answer this,we must consider the quantity of laborand then the quantity of capital.,slide 17,The Marginal Product of Labor,The marginal product of labor(MPL)is the extra amount of output thefirm gets from one extra unit of labor,holding the amount ofcapital fixed and is expressed using the production function:MPL=F(K,L+1)-F(K,L).Most production functions have the property of diminishing marginal product:holding the amount of capital fixed,the marginal product of labor decreases as the amount of labor increases.,Diminishing Marginal Product of Labor,Y,L,The MPL is the change in output when the labor input is increased by 1 unit.As the amount of labor increases,the production function becomes flatter,indicating diminishing marginal product.,slide 18,From the MPL to Labor Demand,When the competitive,profit-maximizing firm isdeciding whether to hire an additional unit of labor,itconsiders how that decision would affect profits.Ittherefore compares the extra revenue from the increasedproduction that results from the added labor to the extracost of higher spending on wages.The increase in revenuefrom an additional unit of labor depends on two variables:the marginal product of labor,and the price of the output.Because an extra unit of labor produces MPL units of outputand each unit of output sells for P dollars,the extra revenueis P MPL.The extra cost of hiring one more unit of laboris the wage W.Thus,the change in profit from hiringan additional unit of labor is D Profit=D Revenue-D Cost=(P MPL)-W,slide 19,Thus,the firms demand for labor is determined by P MPL=W,or another way to express this is MPL=W/P,where W/P is thereal wage the payment to labor measured in units of output ratherthan in dollars.To maximize profit,the firm hires up to the pointwhere the extra revenue equals the real wage.,The MPL depends on the amount of labor.The MPL curve slopes downward becausethe MPL declines as L increases.Thisschedule is also the firms labor demandcurve.,slide 20,The firm decides how much capital to rent in the same way it decideshow much labor to hire.The marginal product of capital,or MPK,is the amount of extra output the firm gets from an extra unit of capital,holding the amount of labor constant:MPK=F(K+1,L)F(K,L).Thus,the MPK is the difference between the amount of output produced with K+1 units of capital and that produced with K units of capital.Like labor,capital is subject to diminishing marginal product.The increase in profit from renting an additional machine is the extrarevenue from selling the output of that machine minus the machinesrental price:D Profit=D Revenue-D Cost=(P MPK)R.To maximize profit,the firm continues to rent more capital until the MPKfalls to equal the real rental price,MPK=R/P.The real rental price of capital is the rental price measured in units of goods rather than in dollars.The firm demands each factor of productionuntil that factors marginal product falls to equal its real factor price.,The MPK and Capital Demand,slide 21,The Division of National Income,The income that remains after firms have paid the factors ofproduction is the economic profit of the firms owners.Real economic profit is:Economic Profit=Y-(MPL L)-(MPK K)or to rearrange:Y=(MPL L)-(MPK K)+Economic Profit.Total income is divided among the returns to labor,the returns to capital,and economic profit.How large is economic profit?If the production function has the propertyof constant returns to scale,then economic profit is zero.This conclusionfollows from Eulers theorem,which states that if the production functionhas constant returns to scale,thenF(K,L)=(MPK K)-(MPL L)If each factor of production is paid its marginal product,then the sumof these factor payments equals total output.In other words,constantreturns to scale,profit maximization,and competition together imply thateconomic profit is zero.,slide 22,Paul Douglas,Paul Douglas observed that the division of national income between capital and labor has beenroughly constant over time.In other words,the total income of workers and the total incomeof capital owners grew at almost exactly thesame rate.He then wondered what conditionsmight lead to constant factor shares.Cobb,a mathematician,said that the production functionwould need to have the property that:,Capital Income=MPK K=Labor Income=MPL L=(1-)Y,slide 23,劳动的需求,假定市场是完全竞争的：即：每个厂商面临的W,R和P 都是给定的基本思想：如果成本小于收益，那么厂商就会增加劳动雇佣。成本=实际工资利润=劳动边际产品价值,slide 24,劳动的边际产品(MPL),定义:厂商运用额外的一单位劳动投入能够生产出来的一单位产出:(假定其它投入不变):MPL=F(K,L+1)F(K,L),slide 25,练习:计算并绘MPL图,计算每一个劳动投入量L上的 MPL 画出生产函数图绘出 MPL 曲线图（其中横轴表示劳动投入量L，纵轴表示MPL）,LYMPL00n.a.110?219?3278434?540?645?749?852?954?1055?,slide 26,答案：,slide 27,Y产出,生产函数与MPL,L劳动,MPL,slide 28,边际报酬递减,随着某种要素投入的增长，它的边际产品价值是递减的(当其它条件不变时)。我们可以直观感觉一下：固定资本K，当投入的劳动L增长时：每个工人拥有的机器数量减少 更低的劳动生产率,slide 29,检查一下你的理解力：,下列那一个生产函数对劳动是边际报酬递减的？,slide 30,第二部分练习,假定 W/P=6。如果厂商现有劳动量 L=3，那么厂商是应该雇佣更多还是更少的劳动？为什么？如果厂商现有劳动量 L=7，那么厂商是应该雇佣更多还是更少的劳动？为什么？,LYMPL00n.a.110102199327843475406645574948523954210551,slide 31,劳动需求与MPL,厂商雇佣劳动的数量达到最佳点时：MPL=W/P,slide 32,租金率的决定,刚才我们已经理解了 MPL=W/P，资本也遵循同样的逻辑 MPK=R/P：资本的边际报酬递减：当使用资本K 时MPK MPK曲线是厂商对资本的需求曲线。厂商利润最大化时拥有的资本量必然使：MPK=R/P。,slide 33,新古典分配理论,每种投入的要素都获得其边际产品价值被许多经济学家所认可,slide 34,收入是如何分配的：,总劳动收入=,如果生产函数是规模报酬不变的，那么：,总资本收入=,slide 35,模型概述,封闭经济，市场出清供给方市场因素(供给，需求，价格)产出/收入的决定因素需求方C,I 和 G 的决定因素均衡商品市场资本借贷市场,DONE,DONE,Next,slide 36,对商品与服务的需求,总需求的组成：C=消费者对g&s的需求I=对投资品的需求G=政府对g&s的需求(封闭经济时：没有净出口NX),slide 37,消费，C,定义：可支配收入是指总收入减去总税收：Y T消费函数：C=C(Y T)表明：(Y T)C 定义：边际消费倾向是指当可支配收入增加一单位时，消费C的增加量,slide 38,消费函数,slide 39,投资，I,投资函数指：I=I(r),这里，r 指实际利率，即名义利率剔除通货膨胀。实际利率是：借款成本 使用自有资本投资时的机会成本。因此，r I,slide 40,投资函数,slide 41,政府支出，G,G 包括政府用于商品与服务上的支出。G 不包括转移支付一般假定政府支出与税收是外生给定的，即：,slide 42,商品与服务市场,实际利率的变化使得需求等于供给。,总需求：,总供给：,均衡：,slide 43,资本借贷市场,一个金融系统的简单的供需模型。将“可借贷的资金”看作一种资产：资金的需求是投资 资金的供给是储蓄 实际利率是资金的“价格”,slide 44,资金的需求：投资,可贷资金的需求:来自投资:厂商为建造厂房、办公大楼以及购置设备、办公用具等而进行的借款融资行为。消费者的购房借款。投资与利率负相关，也即可贷资金的“价格”（借款成本）。,slide 45,资金的需求曲线,投资曲线也就是可贷资金的需求曲线。,slide 46,资金的供给：储蓄,可贷资金的供给来自于储蓄：家庭 把他们的资金存入银行、购买债券及其它资产，从而形成厂商投资时可以借贷的资金。当 政府 获得的税收收入没有全部支出时也会形成储蓄。,slide 47,储蓄的类型,私人储蓄=(Y T)C公共储蓄=T G国民储蓄，S=私人储蓄+公共储蓄=(Y T)C+T G=Y C G,slide 48,符号说明：=变量的变化,对任意变量X，X=“X 的变化量”是希腊字母Delta（大写）,例如：如果 L=1 并且 K=0,那么 Y=MPL。更一般地讲，如果 K=0,那么,(YT)=Y T,因此C=MPC(Y T)=MPC Y MPC T,slide 49,练习：计算储蓄的变化量,假定 MPC=0.8、MPL=20。对于下列每一种情况，计算S：G=100 T=100 Y=100 L=10,slide 50,答案：,slide 51,专栏：预算盈余与预算赤字,当 T G 时，预算盈余=(T G)=公共储蓄当 T G 时，预算赤字=(G T)这时，公共储蓄是负的。当T=G 时，预算平衡，公共储蓄=0。,slide 52,美国联邦政府预算,(T-G)占GDP的百分比,占GDP百分比,slide 53,美国联邦政府赤字,小知识：在 1990 年代早期，每取得1美元税入，大约有18美分用于偿债。(现在，这个数字大约是9美分。),slide 54,可贷资金的供给曲线,国民储蓄并不依赖利率r,因此，供给曲线是垂直的。,slide 55,可贷资金的市场均衡,slide 56,利率 r 的特殊性,r 可使商品市场与资本市场同时达到均衡：如果资本市场是均衡的，那么：Y C G=I 等式两边同时加上(C+G)可得：Y=C+I+G(说明商品市场均衡)因此，,slide 57,专栏：精通模型,要想深入地理解一个模型，必须做到：明确那个变量是内生的，那个变量是外生的。对图形中的每条曲线，应该了解：定义对曲线斜率的直觉所有影响曲线移动的因素运用模型分析2项c目中变量的影响效果。,slide 58,掌握资本市场模型,1.影响储蓄曲线位移因此有：公共储蓄 财政政策：改变 G 或 T公众储蓄偏好税法的设计401条款个人退休帐户（IRA）以消费税替代所得税,slide 59,案例研究：里根时代的赤字,1980年代里根政府的政策：增加国防开支 支出：G 0大力削减税收：T 0依据我们的模型，两大政策都削减了国民储蓄：,slide 60,1.里根时代的赤字，遏制政策,I1,2.进而导致实际利率上升,I2,3.结果是减少了投资水平。,1.赤字的增加减少了储蓄,slide 61,这些数据吻合上面的结论吗?,变量1970s1980sT G2.23.9S19.617.4r1.16.3I19.919.4,TG,S和 I 行的数据表示的是占 GDP的百分比所有这些数据都是过去十年间的平均数。,slide 62,现在，请努力,画出可贷资金模型图。假定税法的调整有利于激励个人储蓄。那么，利率和投资会发生什么变化？(假定税收总额不变),slide 63,掌握可贷资金模型,2.影响投资曲线移动的因素某种技术进步 要利用这种技术进步，公司必须购买新的投资品税法对投资的影响投资税减免,slide 64,投资需求的增长,期望投资增长,r1,slide 65,储蓄与利率,为什么储蓄依赖于利率 r?如果投资需求增加，下列两种情况的结果会有何不同？利率 r 也会同样增长吗？均衡时的投资额会发生什么变化？,slide 66,当储蓄由利率决定时，投资需求的增长,实际利率,r,2.,.,.利率,提高,.,.,投资,储蓄,I,S,S,(,r,),A,B,1.期望,投资增长,.,.,.,3.,.,.均衡时，,投资，储蓄都增长。,I,2,I,1,slide 67,本章总结,总产出决定于经济体中拥有的资本与劳动量技术水平竞争性厂商雇佣要素的最佳点是：要素的边际产品价值等于其价格。如果生产函数是规模报酬不变的，那么，劳动的收入与资本的收入之和就形成总收入（或总产出）。,slide 68,本章总结,经济体的产出被用于消费(决定于可支配收入)投资(取决于实际利率)政府支出(外生变量)实际利率的变化，使得在商品与资本市场上供给等于需求商品与服务可贷资金,slide 69,本章总结,国民储蓄的减少导致利率上升和投资下降。投资需求的增长导致利率的上升，但是，如果可用以借贷的资金不变，则不会影响均衡时的投资水平。,