《宏观经济学（第二版）》课件Ch9 AS－AD模型与经济周期理论

1、第九章ASAD模型与经济周期理论本章主要内容ASAD模型 总供给曲线（Aggregate Supply Curve） 总需求曲线（Aggregate Demand Curve）凯恩斯vs.新古典：两种经济周期理论智者争锋： 萨缪尔森vs.弗里德曼：失而复得的“菲利普斯曲线” 新凯恩斯vs.理性预期：卢卡斯批判“奥肯定律”及其他9.1 ASAD模型 9.1.1 由要素市场均衡推导总需求曲线工资决定与劳动供给：工资决定公式表明：工资与价格预期水平正相关，与失业率负相关，并与工会力量和劳动保护等制度因素正相关： 工资决定公式隐含了就业与实际工资之间的正相关系，即“劳动供给曲线”：9.1 ASAD模型

2、价格决定与劳动需求：价格决定公式表明：商品价格与劳动力成本（即工资水平）正相关，与企业定价能力（即商品市场垄断力量）正相关：价格决定公式隐含了企业的“劳动需求曲线”：9.1 ASAD模型要素（劳动）市场均衡图 9.1 劳动力市场的均衡图 9.2 AS曲线9.1 ASAD模型图 9.3 短期中总供给曲线的移动 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard9.1 ASAD模型图 9.4 总需求曲线的图形推导 9.1.2 由商品市场和金融市场均衡推导总需求曲线总需求曲线向右下方倾斜：财富效应、

3、利率效应汇率效应 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard9.1 ASAD模型市场均衡从短期到中长期的动态调整短期均衡The equilibrium is given by the intersection of the aggregate supply curve and the aggregate demand curve. At point A, the labor market, the goods market, and financial markets are all

4、in equilibrium.In the short run, output can be above or below the natural level of output. 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard图 9.5 市场短期均衡9.1 ASAD模型At point A, 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier BlanchardWage setters will revis

5、e upward their expectations of the future price level. This will cause the AS curve to shift upward.Expectation of a higher price level also leads to a higher nominal wage, which in turn leads to a higher price level.图 9.6 总供给曲线的短期动态调整9.1 ASAD模型The adjustment ends once and wage setters no longer hav

6、e a reason to change their expectations.In the medium run, output returns to the natural level of output 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard图 9.7 总供给曲线的中长期动态调整9.1 ASAD模型中长期均衡图 9.7 市场中长期调整过程9.1 ASAD模型凯恩斯PK新古典经济周期理论周期源起：需求冲击vs.供给冲击？传导机制：价格能否及时调整？宏观政策：调控政策是否必要、是

7、否有效？争论的核心：AS曲线在多大程度上向上倾斜？价格能否得到及时调整？市场能否有效运行？9.2 两种经济周期理论9.2 两种经济周期理论图 9.8 需求冲击与供给冲击对ADAS 曲线的影响凯恩斯PK新古典9.2 两种经济周期理论表 9.1 宏观经济学中对周期现象进行解释的两大学派9.3ASAD 模型中的需求管理政策图 9.9 政府宏观政策的动态调整过程从图（）来看，这两种扩张性政策的效果一样：在短期内都导致AD 曲线向右移动， 均衡点先从A 变到B；随着人们的预期和价格水平得到调整，AS 曲线慢慢向上移动，最后达到长期均衡点C，产出回到自然率水平Y图（）中央银行实行扩张性货币政策，LM 曲线

8、向下移动，物价水平上升，短期均衡从A 点B点。在长期物价水平进一步上升， 相当于实际货币供应量下降， LM 曲线将不断上移， 最后长期均衡回到最初的A 点：产出和利率水平都不变图（）政府实行扩张性财政政策，IS 曲线向右移动。短期均衡将由A 移动到B。随着时间的推移，慢慢向长期均衡点C 移动：产出不变，利率上升表 9.2 政府政策不同政策工具在短期与长期的影响9.3ASAD 模型中的需求管理政策9.3ASAD 模型中的需求管理政策 政策的“时滞”问题 内部时滞：当经济遭受一个外部冲击之后，政府的决策部门要觉察到这一冲击并采取相应措施需要一定的时间，这个时间为内部时滞 外部时滞：政策实施之后经济

9、中的行为人做出反应和调整，使各项宏观经济指标最终达到既定的政策目标又需要一段时间，称为外部时滞 财政政策与货币政策相比，内部时滞要长得多 不同的政策手段外部时滞相差较大9.3ASAD 模型中的需求管理政策图 9.10 美国扩张性货币政策的时滞分析右图是布兰查德（2003） 根据美国1960-1990年的数据所做的研究结果，展示了美联储采取紧缩性的货币政策（例如通过公开市场操作减少基础货币供给）将联邦利率提高，对各宏观经济变量的动态影响。可以看到，对产出、就业和失业率的影响大约在个季度时得到充分显现，但对物价水平的影响要到个季度之后才逐渐显现。根据这一结果，货币政策的外部时滞大约是年半到年。Ho

10、w Long Lasting Are the Real Effects of Money?The Effects of an Expansion in Nominal Money in the Taylor Model 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard9.3ASAD 模型中的需求管理政策图 9.11 政府的需求管理政策：效果的时滞While all 12 models predict that output will increase for some time in res

11、ponse to a monetary expansion, the range of answers regarding the size and the length of the output response is large. 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard图 9.12 政府的需求管理政策：效果的不确定性9.3ASAD 模型中的需求管理政策There is substantial uncertainty about theeffects of policy. 20

12、06 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier BlanchardThere were two sharp increases in the relative price of oil in the 1970s, followed by a decrease in the 1980s and the 1990s.图 9.13 1960 年来的石油价格9.3ASAD 模型中的需求管理政策石油危机、供给冲击与经济滞涨After the increase in the price of oil, the new AS

13、curve goes through point B, where output equals the new lower natural level of output, Yn, and the price level equals Pe.The economy moves along the AD curve, from A to A. Output decreases from Yn to Y. 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard9.3ASAD 模型中的需求管理政策图 9

14、.14 石油危机的短期AS-AD 模型分析Over time, the economy moves along the AD curve, from A to A”.At point A”, the economy has reached the new lower natural level of output, Yn, and the price level is higher than before the oil shock.An increase in the price of oil leads, in the short run, to a decrease in output

15、and an increase in the price level. Over time, output decreases further and the price level increases further. 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard9.3ASAD 模型中的需求管理政策图 9.15 石油危机中“滞涨”模型分析The combination of negative growth and high inflation, or stagnation accomp

16、anied by inflation, is called stagflation. 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard1973 19741975Rate of change of petroleum price (%)10.451.815.1Rate of change of GDP deflator (%)5.69.09.4Rate of GDP growth (%)5.80.6 0.4Unemployment rate (%)4.95.68.59.3ASAD 模型中的需求

17、管理政策表 9.3 1973-1975年石油价格上升造成的影响补充内容：菲利普斯曲线 菲利普斯曲线（Phillips Curve）：Phillips（1958）和Samuelson and Solow（1960）研究发现，一国失业率与通货膨胀率呈反向变动关系 为什么菲利普斯曲线是凯恩斯主义宏观经济学的基石？ 实证研究中发现的“菲利普斯曲线”支持“AS曲线向上倾斜”的理论假说 在政策操作层面，这意味着一国政府可以选择某一“失业率”和“通货膨胀率”的组合作为政策目标，并通过政策操作达到该目标由AS曲线推导出菲利普斯曲线 资料来源：根据布兰查德（2002）图81、82绘制图 9.16 美国19001

18、960年和19481969年的通货膨胀率与失业率关系补充内容：菲利普斯曲线图 9.17 失而复得的“附加预期的菲利普斯曲线”根据布兰查德（2002）图83、85绘制，分别为美国19701998年通胀率（左）和通胀率的变化（右）与失业率的关系。补充内容：菲利普斯曲线失而复得：附加预期的菲利普斯曲线短期和长期的AS曲线与菲利普斯曲线图 9.18 短期和长期的曲线图 9.19 短期和长期的菲利普斯曲线补充内容：菲利普斯曲线根据弗里德曼的思想，宏观经济学中也把通货膨胀预期不变时的失业率，定义为自然失业率在摩擦性失业、结构性失业和周期性失业中，自然失业率是指产出达到自然产出、不存在周期性失业时的失业率水

19、平，此时的经济已经实现了“充分就业”（注意：实现充分就业的经济中仍会存在摩擦性失业和结构性失业。） 补充内容：自然失业率的再讨论The average unemployment rate in Japan since 1960 has been 2.1%, compared to 6.1% in the U.S. One of the main reasons for this difference appears to be the widespread reliance on lifetime employment in the Japanese labor market. Age Gro

20、up16-1920-2425-2955-64Japan0.722.062.714.91United States2.04.406.1510.95 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard各国的“自然失业率”：日本补充内容：自然失业率的再讨论表 9.4 Cumulative Number of Jobs Held by Males of Different Ages, In Japan and the United States.Change in Inflation versus U

21、nemployment: Euro Area since 1961 (Squares denote the 1960s, diamonds the 1970s, triangles the dates since 1980) 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier BlanchardThe Phillips curve relation between the change in the inflation rate and the unemployment rate has shifted to t

22、he right over time, suggesting a steady increase in the natural unemployment rate in Europe since 1960.图 9.20 欧盟国家的菲利普斯曲线各国的“自然失业率”：欧盟补充内容：自然失业率的再讨论Has the U.S. Natural Rate of Unemployment Fallen Since the Early 1990s and, If so, Why? 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivi

23、er BlanchardSince the mid-1990s, the change in inflation has typically been less than would have been predicted by the average relation between inflation and unemployment for the period 1970-2003. 各国的“自然失业率”：美国补充内容：自然失业率的再讨论图 9.21 美国90年代 的菲利普斯曲线公众预期与政策可信性The Lucas critique states that it is unrealis

24、tic to assume that wage setters would not consider changes in policy when forming their expectations.If wage setters could be convinced that inflation was indeed going to be lower than in the past, they would decrease their expectations of inflation, which would in turn reduce actual inflation, with

25、out the need for a change in the unemployment rate. 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard补充内容：卢卡斯批判Thomas Sargent, who worked with Robert Lucas, argued that any in order to achieve disinflation, any increase in unemployment would have to be only small.The essen

26、tial ingredient of successful disinflation, he argued, was credibility of monetary policythe belief by wage setters that the central bank was truly committed to reducing inflation. The central bank should aim for fast disinflation. 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier B

27、lanchard补充内容：卢卡斯批判The actual relation between output growth and the change in the unemployment rate is known as Okuns law.补充内容：奥肯定律（Okuns Law）及其他图 9.22 美国1970年以来失业率与产出的关系 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier BlanchardTo maintain the unemployment rate constant, output gr

28、owth must be 3% per year. This growth rate of output is called the normal growth rate. According to the equation above, output growth 1% above normal leads only to a 0.4% reduction in unemployment, for two reasons:Labor hoarding: firms prefer to keep workers rather than lay them off when output decr

29、eases.When employment increases, not all new jobs are filled by the unemployed. A 0.6% increase in the employment rate leads to only a 0.4% decrease in the unemployment rate. 补充内容：奥肯定律（Okuns Law）及其他Country1960-1980 1981-2003 United States0.390.39United Kingdom0.150.54Germany0.200.32Japan0.020.12The coefficient in Okuns