《宏觀經濟學（第二版）》課件Ch9 AS－AD模型與經濟周期理論

1、第九章ASAD模型與經濟周期理論本章主要內容ASAD模型 總供給曲線（Aggregate Supply Curve） 總需求曲線（Aggregate Demand Curve）凱恩斯vs.新古典：兩種經濟周期理論智者爭鋒： 薩繆爾森vs.弗里德曼：失而復得的“菲利普斯曲線” 新凱恩斯vs.理性預期：盧卡斯批判“奧肯定律”及其他9.1 ASAD模型 9.1.1 由要素市場均衡推導總需求曲線工資決定與勞動供給：工資決定公式表明：工資與價格預期水平正相關，與失業(yè)率負相關，并與工會力量和勞動保護等制度因素正相關： 工資決定公式隱含了就業(yè)與實際工資之間的正相關系，即“勞動供給曲線”：9.1 ASAD模型

2、價格決定與勞動需求：價格決定公式表明：商品價格與勞動力成本（即工資水平）正相關，與企業(yè)定價能力（即商品市場壟斷力量）正相關：價格決定公式隱含了企業(yè)的“勞動需求曲線”：9.1 ASAD模型要素（勞動）市場均衡圖 9.1 勞動力市場的均衡圖 9.2 AS曲線9.1 ASAD模型圖 9.3 短期中總供給曲線的移動 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard9.1 ASAD模型圖 9.4 總需求曲線的圖形推導 9.1.2 由商品市場和金融市場均衡推導總需求曲線總需求曲線向右下方傾斜：財富效應、

3、利率效應匯率效應 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard9.1 ASAD模型市場均衡從短期到中長期的動態(tài)調整短期均衡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圖 9.5 市場短期均衡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.圖 9.6 總供給曲線的短期動態(tài)調整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圖 9.7 總供給曲線的中長期動態(tài)調整9.1 ASAD模型中長期均衡圖 9.7 市場中長期調整過程9.1 ASAD模型凱恩斯PK新古典經濟周期理論周期源起：需求沖擊vs.供給沖擊？傳導機制：價格能否及時調整？宏觀政策：調控政策是否必要、是

7、否有效？爭論的核心：AS曲線在多大程度上向上傾斜？價格能否得到及時調整？市場能否有效運行？9.2 兩種經濟周期理論9.2 兩種經濟周期理論圖 9.8 需求沖擊與供給沖擊對ADAS 曲線的影響凱恩斯PK新古典9.2 兩種經濟周期理論表 9.1 宏觀經濟學中對周期現(xiàn)象進行解釋的兩大學派9.3ASAD 模型中的需求管理政策圖 9.9 政府宏觀政策的動態(tài)調整過程從圖（）來看，這兩種擴張性政策的效果一樣：在短期內都導致AD 曲線向右移動， 均衡點先從A 變到B；隨著人們的預期和價格水平得到調整，AS 曲線慢慢向上移動，最后達到長期均衡點C，產出回到自然率水平Y圖（）中央銀行實行擴張性貨幣政策，LM 曲線

8、向下移動，物價水平上升，短期均衡從A 點B點。在長期物價水平進一步上升， 相當于實際貨幣供應量下降， LM 曲線將不斷上移， 最后長期均衡回到最初的A 點：產出和利率水平都不變圖（）政府實行擴張性財政政策，IS 曲線向右移動。短期均衡將由A 移動到B。隨著時間的推移，慢慢向長期均衡點C 移動：產出不變，利率上升表 9.2 政府政策不同政策工具在短期與長期的影響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“時滯”問題 內部時滯：當經濟遭受一個外部沖擊之后，政府的決策部門要覺察到這一沖擊并采取相應措施需要一定的時間，這個時間為內部時滯 外部時滯：政策實施之后經濟

9、中的行為人做出反應和調整，使各項宏觀經濟指標最終達到既定的政策目標又需要一段時間，稱為外部時滯 財政政策與貨幣政策相比，內部時滯要長得多 不同的政策手段外部時滯相差較大9.3ASAD 模型中的需求管理政策圖 9.10 美國擴張性貨幣政策的時滯分析右圖是布蘭查德（2003） 根據美國1960-1990年的數據所做的研究結果，展示了美聯(lián)儲采取緊縮性的貨幣政策（例如通過公開市場操作減少基礎貨幣供給）將聯(lián)邦利率提高，對各宏觀經濟變量的動態(tài)影響?？梢钥吹?，對產出、就業(yè)和失業(yè)率的影響大約在個季度時得到充分顯現(xiàn)，但對物價水平的影響要到個季度之后才逐漸顯現(xiàn)。根據這一結果，貨幣政策的外部時滯大約是年半到年。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圖 9.11 政府的需求管理政策：效果的時滯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圖 9.12 政府的需求管理政策：效果的不確定性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.圖 9.13 1960 年來的石油價格9.3ASAD 模型中的需求管理政策石油危機、供給沖擊與經濟滯漲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圖 9

14、.14 石油危機的短期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圖 9.15 石油危機中“滯漲”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年石油價格上升造成的影響補充內容：菲利普斯曲線 菲利普斯曲線（Phillips Curve）：Phillips（1958）和Samuelson and Solow（1960）研究發(fā)現(xiàn)，一國失業(yè)率與通貨膨脹率呈反向變動關系 為什么菲利普斯曲線是凱恩斯主義宏觀經濟學的基石？ 實證研究中發(fā)現(xiàn)的“菲利普斯曲線”支持“AS曲線向上傾斜”的理論假說 在政策操作層面，這意味著一國政府可以選擇某一“失業(yè)率”和“通貨膨脹率”的組合作為政策目標，并通過政策操作達到該目標由AS曲線推導出菲利普斯曲線 資料來源：根據布蘭查德（2002）圖81、82繪制圖 9.16 美國19001

18、960年和19481969年的通貨膨脹率與失業(yè)率關系補充內容：菲利普斯曲線圖 9.17 失而復得的“附加預期的菲利普斯曲線”根據布蘭查德（2002）圖83、85繪制，分別為美國19701998年通脹率（左）和通脹率的變化（右）與失業(yè)率的關系。補充內容：菲利普斯曲線失而復得：附加預期的菲利普斯曲線短期和長期的AS曲線與菲利普斯曲線圖 9.18 短期和長期的曲線圖 9.19 短期和長期的菲利普斯曲線補充內容：菲利普斯曲線根據弗里德曼的思想，宏觀經濟學中也把通貨膨脹預期不變時的失業(yè)率，定義為自然失業(yè)率在摩擦性失業(yè)、結構性失業(yè)和周期性失業(yè)中，自然失業(yè)率是指產出達到自然產出、不存在周期性失業(yè)時的失業(yè)率水

19、平，此時的經濟已經實現(xiàn)了“充分就業(yè)”（注意：實現(xiàn)充分就業(yè)的經濟中仍會存在摩擦性失業(yè)和結構性失業(yè)。） 補充內容：自然失業(yè)率的再討論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各國的“自然失業(yè)率”：日本補充內容：自然失業(yè)率的再討論表 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.圖 9.20 歐盟國家的菲利普斯曲線各國的“自然失業(yè)率”：歐盟補充內容：自然失業(yè)率的再討論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. 各國的“自然失業(yè)率”：美國補充內容：自然失業(yè)率的再討論圖 9.21 美國90年代 的菲利普斯曲線公眾預期與政策可信性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補充內容：盧卡斯批判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補充內容：盧卡斯批判The actual relation between output growth and the change in the unemployment rate is known as Okuns law.補充內容：奧肯定律（Okuns Law）及其他圖 9.22 美國1970年以來失業(yè)率與產出的關系 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. 補充內容：奧肯定律（Okuns Law）及其他Country1960-1980 1981-2003 United States0.390.39United Kingdom0.150.54Germany0.200.32Japan0.020.12The coefficient in Okuns