单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,第四章,产品市场和货币市场的一般均衡,Determination of National Income:,The ISLM Model,11/20/2024,1,Learning Objectives,In this chapter,you will learn about:,Determination of Investment,The goods market and the IS relation,Money market and the LM relation,The ISLM model,A framework of Keynes theory,11/20/2024,2,第一节：投资的决定,In chapter 2 and 3,we defined national income as the sum of consumption,investment,government spending,and net export.The main simplification of the identity was that the interest rate did not affect investment.Our first task in this chapter is to remove this simplification and discussion of the effect of the interest rate on investment.,11/20/2024,3,一、投资函数,（,Investment Function,）,Investment depends on primarily on two factors:,The level of sales.A firm facing an increase in sales needs to increase production.A firm facing low sales will feel no such need and spending little on investment,The interest rate.The higher the interest rate,the less likely the firm is to borrow and buy the machine.,11/20/2024,4,投资取决于实际利率,名义利率（,nominal interest rate,）：银行支付的利率，即：没有根据通货膨胀调整的借贷的成本。,实际利率（,real interest rate,）：根据通货膨胀调整之后的借贷的成本。,费雪方程式（,Fisher equation,）：,r=i-,(r,代表实际利率，,i,代表名义利率，,代表通货膨胀率）,投资大小取决于实际利率的高低：,i=,i(r,),，投资与实际利率成负相关。,11/20/2024,5,二、资本的边际效率,Marginal efficiency of capital:,That unique,rate of discount which would make the present value of the expected net returns from a capital asset just equal to its supply price when there is no rise in the supply price of the asset.,Rate of discount:,The interest rate used to discount a sequence of future payments.,11/20/2024,6,一项投资未来收益的现值与利率高低有关：,上式的,PV,代表现值，,i,代表利率（也就是投资者的预期利润率），如果有一个,i,使得这个等式成立，这个,i,就是,MEC,。（见课本,P.477,的例子）,11/20/2024,7,资本的边际效率（,MEC,）与投资的边际效率（,Marginal efficiency of investment,MEI,）的区别：,The MEI takes specific account of the fact that the supply price of capital assets will rise in the short run as all firms simultaneously seek to increase the size of their capital stock.,MEI,也被称为,internal rate of return,，它更准确表达投资与利率之间的关系。,11/20/2024,8,第二节：,IS,曲线,从简单的国民收入决定理论得知，在两部门经济中，产品市场的均衡条件是：,S=I,。根据这个条件，可以推导出,IS,曲线，即产品市场均衡的曲线，该曲线说明：在产品市场均衡条件下，收入水平,Y,和利率水平,r,之间的关系：,An increase in the interest rate decrease investment.The decrease in investment leads to decrease in output,which further decrease consumption and investment.In other words,the initial decrease in investment leads to a larger decrease in output through the multiplier effect.,11/20/2024,9,一、,IS,曲线及其推导,1,、用公式法推导,IS,曲线（,The derivation of the IS curve,）,（参阅教材第,481,482,页）,假定：两部门经济、投资函数为：,i=e,dr,均衡条件：,y=(,e,dr)/1,从以上均衡条件可以看出，,、,、,e,、,d,都是参数，只有,r,和,y,是未知数。所以，只要确定出一个未知数的数值，另一个未知数就能求出来。,根据,y,和,r,的组合在坐标图上画出的曲线就称为,IS,曲线。,11/20/2024,10,2,、用图像法推导,IS,曲线,（参阅教材第,482,483,页）,11/20/2024,11,二、,IS,曲线的斜率,(Slope of the IS curve,）,可见，,IS,曲线的斜率与边际消费倾向有关，也与投资的利率弹性有关。总的来说，边际消费倾向越大，,IS,曲线的斜率就越小；投资的利率弹性越大，,IS,曲线的斜率越小。,11/20/2024,12,三、,IS,曲线的移动,（,Shifts in the IS curve),i,和,g,的增加，将会使,IS,曲线向右移动，,y,增加；反之，,i,和,g,的减少，将会使,IS,曲线向左移动，,y,减少。,s,和,t,的增加，将会使,IS,曲线向左移动，,y,减少；反之，,s,和,t,的减少，将会使,IS,曲线向右移动，,y,增加。,有关例子，请参阅教材第,485,487,页。,11/20/2024,13,11/20/2024,14,11/20/2024,15,Summarize of Goods Market,Equilibrium in the goods market implies that output is a decreasing function of the interest rate.,This relation is represented by the downward-sloping IS curve.,Change in factors that decrease or increase the demand for goods given the interest rate shift the IS curve to the left or to the right.,11/20/2024,16,第三节：利率的决定,一、利率的决定（,The determination of the interest rate,）,The interest rate is determined by the quantity of the supply of money and the demand for money.,By changing the supply of money,the central bank can affect the interest rate.,In developed countries,the central bank changes the supply of money through open market operation,which are purchases or sales of bonds for money.,11/20/2024,17,二、货币需求动机与货币需求函数,1,、货币需求动机,凯恩斯认为，人们之所以对货币产生需求（,demand for money,），主要有三个动机（,motive,）：,Transaction motive,Precautionary motive,Speculative motive,前两个动机主要取决于,y,的大小，并且与,y,正相关，记为：或,11/20/2024,18,第三个动机主要与,r,有关，而且与,r,存在负相关，记为：,为什么对货币的投机性需求与利率负相关？,1,）假设投机者只有货币和债券两种资产可选择；,2,）预期利率的变动将会对投机者的资产选择产生影响，投资者心中必有一,“,标准利率水平,”,；,3,）存在以下关系：债券价格债券收益,/,利率。,11/20/2024,19,2,、货币需求函数,实际货币需求函数可以表示为：,货币市场的均衡条件可以表示为：,与 和 相对应，,M,也划分为 和,11/20/2024,20,三、流动偏好陷阱,Liquidity preference:,The term introduced by Keynes to denote the demand for money.,Liquidity trap,（,Keynesian trap,）,:,The case where nominal interest rate are close to zero,and monetary policy cannot therefore decrease them further.,r,L,、,M,O,L,11/20/2024,21,第四节：,LM,曲线,一、,LM,曲线及其推导,1,、用公式法推导,LM,曲线（参阅第,494,495,页）,从货币市场的均衡条件可以推导出：,这个公式中的,k,、,h,是参数，,M,是外生变量，只有,y,和,r,是未知数，所以，只要能确定其中任何一个未知数，另一个未知数就可以求出来。,根据,y,和,r,的组合在坐标图上画出的曲线就称为,LM,曲线。,11/20/2024,22,2,、用图象法推导,LM,曲线,（参阅,495,497,页）,11/20/2024,23,二、,LM,曲线的斜率,根据,其中,k/h,就是,LM,曲线的斜率。这说明，如果货币需求的利率弹性越大（,h,），则,LM,曲线越平缓，当利率降得很低的时候，货币需求的利率弹性变得无穷大，这就进入了“流动陷阱”；另一方面，如果货币需求的收入弹性越大（,k,），则,LM,曲线越陡峭。,LM,曲线得斜率主要取决于货币需求的利率弹性，即：取决于货币的投机需求函数。,11/20/2024,24,LM,曲线的三个区域