资源描述
Learning ObjectivesIn this chapter,you will learn about:oDetermination of InvestmentoThe goods market and the IS relationoMoney market and the LM relationoThe ISLM modeloA framework of Keynes theory7/17/20241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.7/17/20242一、投资函数(Investment Function)Investment depends on primarily on two factors:oThe 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 investmentoThe interest rate.The higher the interest rate,the less likely the firm is to borrow and buy the machine.7/17/20243投资取决于实际利率o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。o实际利率(real interest rate):根据通货膨胀调整之后的借贷的成本。o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)o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。7/17/20244二、资本的边际效率oMarginal 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.oRate of discount:The interest rate used to discount a sequence of future payments.7/17/20245o一项投资未来收益的现值与利率高低有关:o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)7/17/20246o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。7/17/20247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.7/17/20248一、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481482页)o假定:两部门经济、投资函数为:i=edro均衡条件:y=(edr)/1o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。o根据y 和r的组合在坐标图上画出的曲线就称为IS曲线。7/17/202492、用图像法推导IS曲线(参阅教材第482483页)7/17/202410二、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。7/17/202411三、IS曲线的移动(Shifts in the IS curve)oi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。os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。o有关例子,请参阅教材第485487页。7/17/2024127/17/2024137/17/202414Summarize of Goods MarketoEquilibrium in the goods market implies that output is a decreasing function of the interest rate.oThis relation is represented by the downward-sloping IS curve.oChange 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.7/17/202415第三节:利率的决定一、利率的决定(The determination of the interest rate)oThe interest rate is determined by the quantity of the supply of money and the demand for money.oBy changing the supply of money,the central bank can affect the interest rate.oIn developed countries,the central bank changes the supply of money through open market operation,which are purchases or sales of bonds for money.7/17/202416二、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):oTransaction motiveoPrecautionary motiveoSpeculative 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7/17/202417o第三个动机主要与r有关,而且与r存在负相关,记为:o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。7/17/2024182、货币需求函数o实际货币需求函数可以表示为:o货币市场的均衡条件可以表示为:o与 和 相对应,M也划分为 和7/17/202419三、流动偏好陷阱oLiquidity preference:The term introduced by Keynes to denote the demand for money.oLiquidity trap(Keynesian trap):The case where nominal interest rate are close to zero,and monetary policy cannot therefore decrease them further.rL、MOL7/17/202420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494495页)o从货币市场的均衡条件可以推导出:o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。o根据y 和r的组合在坐标图上画出的曲线就称为LM曲线。7/17/2024212、用图象法推导LM曲线(参阅495497页)7/17/202422二、LM曲线的斜率o根据o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。oLM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。7/17/202423LM曲线的三个区域7/17/202424三、LM曲线的移动o在其他条件不变的情况下,如果货币需求增加(表现为 线向左边移动,或 线向右边移动),LM线会向左边移动,y下降,反之亦然。o在其他条件不变的情况下,如果货币供给增加(表现为M线向右移动),LM曲线会向右边移动,y上升,反之亦然。7/17/2024257/17/202426第五节:ISLM分析 如前所示,IS曲线上的每一点都表示产品市场的均衡,LM曲线上的每一点都表示货币市场的均衡。但是,在产品市场上,想要知道y,就必须首先知道r,而r是在货币市场上由货币的供求决定的。在货币市场上,如果不确定y,又无法知道r。这样,如果把产品市场和货币市场分开,就会陷入一个循环推论。建立ISLM模型,循环推论的难题就可以解决。7/17/202427一、两个市场同时均衡的利率和收入1、用公式法解出均衡值投资函数:储蓄函数:货币需求函数:货币供应量:均衡条件:7/17/2024282、用图象法解出均衡值ELMISroyYR7/17/2024293、失衡及其自动调节失衡区域o在IS线的左边,存在I大于S,在IS线的右边,存在I小于S;o在LM线的左边,存在L小于M,在LM线的右边,存在L大于M。ISLM rOY7/17/202430失衡状况7/17/202431失衡的自动调节o单从产品市场考虑,IS的不均衡会导致收入的变动:当IS时,会导致Y的上升,当IS时,会导致Y的下降。o同样,单独从货币市场来考虑,LM的不均衡会导致利率的变动,当ML时,会导致利率下降,当ML时,会导致利率的上升。o综合起来考虑,产品市场的不均衡,会引起收入和利率的不断调整,最后达到两个市场的同时均衡;但是,如果没有政府干预,这个过程会很长。7/17/202432自动调节图示AroyLMISE7/17/202433二、均衡收入和利率的变动 shift in IS shift in LM movement movement in in output interest rate Increase in taxes left none down down Decrease in taxes right none up upIncrease in spending right none up upDecrease in spending left none down downIncrease in money none down up downDecrease in money none up down up 7/17/2024347/17/202435第六节:凯恩斯的基本理论框架7/17/2024367/17/202437 The End7/17/202438谢谢!谢谢!3940
展开阅读全文