Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Click to edit Master title style,第九章 经济波动简介,slide,*,本章目的,长期与短期的差异,介绍总需求,长期与短期总供给,理解如何运用总供给与总需求曲线分析长期与短期的“冲击”效应,0,美国实际GDP的增长,平均增长率=3.5%,1,Short-run fluctuations in output and employment are called the,business cycle.,In previous chapters,we developed theories to explain how the economy behaves in the long run;now well seek to understand how the economy behaves in the short run.,The Business Cycle,2,GDP and Its Componants,GDP is the first place to start when analyzing the business cycle,since it is the largest gauge of economic conditions.,The National Bureau of Economic Research(NBER)is the official,determiner of whether the economy is suffering from a recession.,A,recession,is usually defined by a period in which there are two,consecutive declines in real GDP.,In recessions,both consumption and investment decline;however,investment(business equipment,structures,new housing and,inventories)is even more susceptible to decline.,3,Okuns Law,Okuns Law,In recessions,unemployment rises.This negative(when one rises,the other falls)relationship between unemployment and GDP is called,Okuns Law,after Arthur Okun,the economist who first studied it.In short,it is defined as:,Percentage Change in Real GDP=,3.5%-2,the Change in the Unemployment Rate,If the unemployment rate remains the same,real GDP grows by,about 3.5 percent.For every percentage point the unemployment rate,rises,real GDP growth typically falls by 2 percent.Hence,if the,unemployment rate rises from 5 to 8 percent,then real GDP growth,would be:,Percentage Change in Real GDP=3.5%-2,(8%-5%)=-2.5%,In this case,GDP would fall by 2.5%,indicating that the economy,is in a recession.,4,Leading Economic Indicators,Many economists in business and government have the role,of forecasting short-run fluctuations in the economy.One way,that economists arrive at forecasts is through looking at,leading,indicators.,Each month,the Conference Board,a private economics,Research announces the,index of leading economic indicators,which consists of 10 data series.,5,Index of Leading Economic Indicators,Average workweek of production workers in manufacturing,Average initial weekly claims for unemployment insurance,New orders for consumer goods and materials adjusted for inflation,New orders,nondefense capital goods,Vendor performance,New building permits issued,Index of stock prices,Money-supply(,M,2)adjusted for inflation,Interest rate spread:the yield spread between 10-year Treasury,notes and 3-month treasury bills,10)Index of consumer expectations,6,时间范围,长期：价格是柔性，随供需变化而变化,短期：在某一预定水平上价格是“刚性或粘性”的,当价格是粘性时，经济行为大不一样。,7,在古典宏观经济理论中，,(我们在第3-8章已学习过),产出由供给方打算：,资本与劳动的供给,技术,对商品与效劳(C,I,G)的需求仅仅影响价格而不影响数量。,完全的价格柔性是一个重要的假设，因此，古典理论适用于长期。,8,当价格粘性时，,产出与就业同样依靠于对商品与效劳的需求，,它受下面因素影响：,财政政策(政府支出G 与 税收T),货币政策(M),其它因素，如在 C 或 I 上的外生变化,9,总供需模型,大多数经济学家和政策制定者有以考虑经济波动与经济稳定政策范例,说明价格水平与总产出是如何打算的,说明长期与短期的经济行为有何区分,10,总需求,总需求曲线表示价格水平与需求产出量间的关系。,为了介绍本章的 AD/AS 模型，我们使用一个简洁的基于货币数量论的总需求理论。,第10-12 章，更具体地进展了这个总需求理论。,11,基于数量方程的总需求函数,回忆第四章的数量方程：,M V =P Y,及其隐含的货币需求函数：,(M/P)d=k Y这里 V=1/k=货币流通速度。,对于给定的 M 与 V 值，方程说明P、Y之间存在负相关关系：,12,向下倾斜的,AD,曲线,价格水平的上升导致实际货币余额的下降(M/P)，,导致对商品与效劳需求的下降。,Y,P,AD,13,AD,曲线的移动,货币供给增加，AD曲线向右移动。,Y,P,AD,1,AD,2,14,长期总供给,回忆第三章：在长期中，产出由生产要素的供给及技术状况打算：,是,充分就业,或者,自然,的产出水平，这时，经济中的资源得到了充分的利用。,“充分就业”意味着失业率等于自然失业率。,15,长期总供给,回忆第三章：在长期中，产出由生产要素的供给及技术状况打算：,充分就业时的产出并不依靠于价格水平，,因此，长期总供给曲线(LRAS，the long run aggregate supply)是垂直的：,16,长期总供给曲线,Y,P,LRAS,在充分就业产出水寻常，LRAS曲线是垂直的。,17,M,增长的长期效应,Y,P,AD,1,AD,2,LRAS,M,增长，使,AD,曲线向右移动,P,1,P,2,长期看，价格水平是上涨的,但是产出一样,18,短期总供给,现实世界中，从短期看，很多价格是粘性的。,既然这样(从9-12章)，在短期内，我们假定全部的价格水平都是预先给定的，是粘性的,并且，厂商情愿供给在那样的价格水平上的消费者所能购置的数量,因此，短期的总供给曲线(SRAS，short-run aggregate supply)是水平的：,19,短期总供给曲线,Y,P,SRAS,SRAS 曲线是水平的：,价格水平固定在预先确定的水平上，厂商能够满足消费者在这一价格水平上的需求。,20,M,增加的短期效应,Y,P,AD,1,AD,2,总需求的增加,短期价格水平是粘性的，,导致产出增加。,SRAS,Y,2,Y,1,21,从短期到长期,经过一段时间，价格渐渐变成“非粘性”的。这时，它们是上升还是下降？,上升,下降,不变,短期均衡时，假设,那么，经过一段时间价格水平将,这种价格水平的调整，使得经济趋向长期均衡。,22,M,0,时的 SR&LR 效应,Y,P,AD,1,AD,2,LRAS,SRAS,P,2,Y,2,A=,初始均衡点,A,B,C,B=Fed,增加,M,时，新的短期均衡点,C=,长期均衡,23,如何冲击!,冲击：外生变量造成的总供需的变化,冲击使经济临时性地偏离充分就业状态。,一个需求冲击的例子：外生变量造成货币流通速度下降,假设货币供给不变，那么，V 的下降意味着人们将较少地使用他们的货币进展交易，这样会导致对商品与效劳需求的削减：,24,LRAS,AD,2,SRAS,需求冲击的负效应,Y,P,AD,1,P,2,Y,2,冲击使AD曲线左移，结果使短期的就业与产出降低。,A,B,C,经过一段时间，价格水平下降，经济沿着其需求曲线下移到充分就业时的水平。,25,供给冲击,A,supply shock,alters production costs,affects the prices that firms charge.(also called,price shocks,),Examples of,adverse,supply shocks:,Bad weather reduces crop yields,pushing up food prices.,Workers unionize,negotiate wage increases.,New environmental regulations require firms to reduce emissions.Firms charge higher prices to help cover the costs of compliance.,(,Favorable,supply shocks,lower,costs and prices.),26,案例争论：1970年月的石油危机,1970年月早期：OPEC 成员协调形成了一个削减石油供给的打算。,油价上升：1973年上升11%1974年上升68%1975年上升16%,如此快速的油价上升，对供供方造成了巨大冲击，由于石油价格对产品本钱及价格有着重要的影响。,27,SRAS,1,Y,P,AD,LRAS,Y,2,油价冲击促使 SRAS 上移，造成产出与就业的下降。,A,B,假设没有进一步的油价冲击，经过一段时间以后，价格就会充分就业时的水平。,SRAS,2,案例争论：1970年月的石油危机,A,28,案例争论：1970年月的石油