经济波动导论.ppt

第九章 经济波动导论,本章从三个任务开始：我们考察描述短期经济波动的数据；讨论经济的长期行为和短期行为之间的关键区别；引入总供给和总需求模型。,9.1 关于经济周期的事实,经济学家把产出与就业的短期波动称为经济周期，前面的章节中我们建立了解释经济在长期中的行为的理论，现在来看看经济学家如何解释短期经济波动。在思考之前，我们首先看看描述短期波动的一些事实。,GDP growth averages 33.5 percent per year over the long run with large fluctuations in the short run.Consumption and investment fluctuate with GDP,but consumption tends to be less volatile and investment more volatile than GDP.,GDP及其构成,Growth rates of real GDP,consumption,Percent change from 4 quarters earlier,Growth rates of real GDP,consumption,investment,Percent change from 4 quarters earlier,经济周期不仅清楚反映在国民收入账户的数据中，也反映在表示劳动市场状况的数据中。失业率与GDP之间的这一负相关关系被称为奥肯定律。通过散点画出的曲线告诉我们：Percentage Change in Real GDP=3.5%-2 the Change in the Unemployment Rate,失业率,Percent of labor force,Okuns Law,Percentage change in real GDP,Change in unemployment rate,1975,1982,1991,2001,1984,1951,1966,2003,1987,2008,1971,许多经济学家都有着预测经济的短期波动的任务，经济学家得到预测结果的一种方法是观察领先指标，这些变量的波动往往先于整体经济。美国经济咨询局一个私立经济研究机构都公布领先经济指标指数。,领先经济指标,Average workweek of production workers inmanufacturingAverage initial weekly claims for unemployment insuranceNew orders for consumer goods and materials adjusted for inflationNew orders,nondefense capital goodsVendor performanceNew building permits issuedIndex of stock pricesMoney-supply(M2)adjusted for inflationInterest rate spread:the yield spread between 10-year Treasurynotes and 3-month treasury bills10)Index of consumer expectations,Index of Leading Economic Indicators,短期和长期有什么不同长期：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,9.2 宏观经济学的时间范围,当价格是粘性时，经济行为大不相同。,总供给与总需求模型,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，我们使用一个简单但不完全的基于货币数量论的总需求理论。第10-12 章，更详细地发展了这个总需求理论。,9.3 总需求,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，方程表明P、Y之间存在负相关关系：,作为总需求的数量方程,总需求曲线,价格水平的上升导致实际货币余额的下降(M/P)，导致对商品与服务需求的下降。,Think about the supply and demand for real money balances.If output is higher,people engage in more transactions and need higher real balances M/P.For a fixed money supply M,higher real balances imply a lower price level.Conversely,if the price level is lower,real money balances are higher;the higher level of real balances allows a greater volume oftransactions,which means a greater quantity of output is demanded.,Why the aggregate demand curve slopes downward,Shifts in Aggregate Demand,Shifts in Aggregate Demand,9.4 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决定：充分就业时的产出并不依赖于价格水平，因此，长期总供给曲线(LRAS，the long run aggregate supply)是垂直的：,The vertical line suggests that changes in the price level will have no lasting impact onfull employment.,P,Y,Y,Y=F(K,L),LRAS,Long-run effects of an increase in M,An increase in M shifts AD to the right.,P1,现实世界中，从短期看，许多价格是粘性的。既然这样(从9-12章)，在短期内，我们假定所有的价格水平都是预先给定的，是粘性的 并且，厂商愿意供给在那样的价格水平上的消费者所能购买的数量因此，短期的总供给曲线(SRAS，short-run aggregate supply)是水平的：,短期：水平的总供给曲线,The short-run aggregate supply curve,The SRAS curve is horizontal:The price level is fixed at a predetermined level,and firms sell as much as buyers demand.,Short-run effects of an increase in M,Y1,an increase in aggregate demand,rise,fall,remain constant,In the short-run equilibrium,if,then over time,P will,The adjustment of prices is what moves the economy to its long-run equilibrium.,从短期到长期,P,Y,LRAS,Y,Y=F(K,L),AD,SRAS,The Long-run Equilibrium,In the long run,the economy finds itself at the intersection of thelong-run aggregate supply curve and aggregate demand curve.Becauseprices have adjusted to this level,the SRAS crosses this point as well.,A Reduction in Aggregate Demand,P,Y,LRAS,Y,AD,SRAS,AD,A,B,C,The economy begins in long-run equilibrium at point A.Then,a reduction in aggregate demand,perhaps caused by a decrease in the money supply M,moves the economy from point A to point B,whereoutput is below its natural level.As prices fall,the economy recovers from the recession,moving from point B to point C.,经济学家把使总供给或总需求曲线移动的外生事件称为对经济的冲击。总供给与总需求模型的一个目的是说明这些冲击如何影响经济波动。这个模型的另一个目的是评价宏观经济政策可以如何对这些冲击做出反应，这种政策也被称为稳定化政策。,9.5 稳定化政策,P,Y,LRAS,Y,AD,SRAS,AD,A,B,C,Shocks to Aggregate Demand,The economy begins in long-run equilibrium at point A.An increasein aggregate demand,due to an increase in the velocity of money,moves the economy from point A to point B,where output is aboveits natural level.As prices rise,output gradually returns to its naturalrate,and the economy moves from point B to point C.,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 pliance.Favorable supply shocks lower costs and prices,Shocks to Aggregate Demand,案例研究：1970年代的石油危机,1970年代早期：OPEC 成员协调形成了一个减少石油供应的计划。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，因为石油价格对产品成本及价格有着重要的影响,CASE STUDY:The 1970s oil shocks,The oil price shock shifts SRAS up,causing output and employment to fall.,A,B,In absence of further price shocks,prices will fall over time and economy moves back toward full employment.,A,Stabilizing output with monetary policy,B,A,C,But the Fed acmodates the shock by raising agg.demand.,results:P is permanently higher,but Y remains at its full-employment level.,