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1、macroeconomics fifth editionN. Gregory MankiwPowerPoint Slides by Ron CronovichCHAPTER NINEIntroduction to Economic Fluctuationsmacro 2002 Worth Publishers, all rights reservedCHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 1Chapter objectivesdiffe
2、rence between short run & long runintroduction to aggregate demandaggregate supply in the short run & long runsee how model of aggregate supply and demand can be used to analyze short-run and long-run effects of “shocks”CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economi
3、c Fluctuationsslide 2Real GDP Growth in the United StatesAverage growth rate = 3.5%CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 3Time horizonsLong run: Prices are flexible, respond to changes in supply or demandShort run:many prices are “sticky”
4、 at some predetermined levelThe economy behaves much differently when prices are sticky.CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 4In Classical Macroeconomic Theory,(what we studied in chapters 3-8)Output is determined by the supply side:supp
5、lies of capital, labortechnologyChanges in demand for goods & services (C, I, G ) only affect prices, not quantities.Complete price flexibility is a crucial assumption,so classical theory applies in the long run.CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctu
6、ationsslide 5When prices are stickyoutput and employment also depend on demand for goods & services,which is affected byfiscal policy (G and T )monetary policy (M )other factors, like exogenous changes in C or I. CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluct
7、uationsslide 6The model of aggregate demand and supplythe paradigm that most mainstream economists & policymakers use to think about economic fluctuations and policies to stabilize the economy shows how the price level and aggregate output are determinedshows how the economys behavior is different i
8、n the short run and long runCHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 7Aggregate demandThe aggregate demand curve shows the relationship between the price level and the quantity of output demanded. For this chapters intro to the AD/AS model,
9、we use a simple theory of aggregate demand based on the Quantity Theory of Money. Chapters 10-12 develop the theory of aggregate demand in more detail. CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 8The Quantity Equation as Agg. DemandFrom Chapte
10、r 4, recall the quantity equationM V = P Y and the money demand function it implies:(M/P )d = k Ywhere V = 1/k = velocity.For given values of M and V, these equations imply an inverse relationship between P and Y:PYAD总需求CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economi
11、c Fluctuationsslide 9The downward-sloping AD curveAn increase in the price level causes a fall in real money balances (M/P ),causing a decrease in the demand for goods & services.Y PADCHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 10Shifting the A
12、D curveAn increase in the money supply shifts the AD curve to the right. Y PAD1AD2为什么价格下降，总需求增加？这里不存在替代效用，因为所有的商品价格都上升。也不存在收入效应，应为工资也相应减少。实际上是价格上升，在货币供给不变的前提下，实际货币供给（M/P）减少（price shock），导致利率上升，LM曲线左移，总需求减少。CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuations
13、slide 11Aggregate Supply in the Long RunRecall from chapter 3: In the long run, output is determined by factor supplies and technologyis the full-employment or natural level of output, the level of output at which the economys resources are fully employed.“Full employment” means that unemployment eq
14、uals its natural rate.CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 12Aggregate Supply in the Long RunRecall from chapter 3: In the long run, output is determined by factor supplies and technologyFull-employment output does not depend on the pric
15、e level,so the long run aggregate supply (LRAS) curve is vertical:CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 13The long-run aggregate supply curveY PLRASThe LRAS curve is vertical at the full-employment level of output. CHAPTER 9CHAPTER 9 Intr
16、oduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 14Long-run effects of an increase in MY PAD1AD2LRASAn increase in M shifts the AD curve to the right. P1P2In the long run, this increases the price levelbut leaves output the same.所有刺激性的经济政策，在长期中只能推动物价增长CHAPTER 9CHAPTER 9 I
17、ntroduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 15Aggregate Supply in the Short RunIn the real world, many prices are sticky in the short run. For now (and throughout Chapters 9-12), we assume that all prices are stuck at a predetermined level in the short run and tha
18、t firms are willing to sell as much as their customers are willing to buy at that price level. Therefore, the short-run aggregate supply (SRAS) curve is horizontal:CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 16The short run aggregate supply cur
19、veY PSRASThe SRAS curve is horizontal:The price level is fixed at a predetermined level, and firms sell as much as buyers demand.短期是可以加班的，一旦价格上升，企业立刻加班CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 17Short-run effects of an increase in MY PAD1AD2a
20、n increase in aggregate demandIn the short run when prices are sticky,causes output to rise.SRASY2Y1CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 18From the short run to the long runOver time, prices gradually become “unstuck.” When they do, will
21、 they rise or fall? risefallremain constantIn the short-run equilibrium, ifthen over time, the price level willThis adjustment of prices is what moves This adjustment of prices is what moves the economy to its long-run equilibrium.the economy to its long-run equilibrium.Yba 是自然增长率，Y是实际增长率目前的CPI低估物价上
22、涨速度，因为CPI计入房租而不计入房价，将住房考虑进去之后，CPI可能会再增加3个百分点。有可能中国的自然增长率应该是6%而我们一直维持在8%的水平，结果就是物价上涨CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 19The SR & LR effects of M 0Y PAD1AD2LRASSRASP2Y2A = initial equilibriumABCB = new short-run eqm after Fed increases
23、MC = long-run equilibrium需求增加：政策因素，外部冲击例如战争。从短期到长期，物价慢慢上涨，实际货币供给减少，总供给回归到自然增长率水平能不能做到持续增加货币供给，维持实际货币供给不变，保证总供给不回调？不能，因为人们会有预期。不可能不断的刺激货币供给CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 20How shocking!shocks: exogenous changes in aggregate supply o
24、r demandShocks temporarily push the economy away from full-employment.An example of a demand shock:exogenous decrease in velocity If the money supply is held constant, then a decrease in V means people will be using their money in fewer transactions, causing a decrease in demand for goods and servic
25、es:信用卡诈骗会使人们更多的用现金交易，导致velocity减少CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 21LRASAD2SRASThe effects of a negative demand shockY PAD1P2Y2The shock shifts AD left, causing output and employment to fall in the short runABCOver time, prices fall
26、and the economy moves down its demand curve toward full-employment.CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 22Supply shocksA supply shock alters production costs, affects the prices that firms charge. (also called price shocks)Examples of ad
27、verse 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.
28、) CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 23CASE STUDY: The 1970s oil shocksEarly 1970s: OPEC coordinates a reduction in the supply of oil.Oil prices rose11% in 1973 68% in 1974 16% in 1975Such sharp oil price increases are supply shocks be
29、cause they significantly impact production costs and prices.CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 24SRAS1Y PADLRASY2The oil price shock shifts SRAS up, causing output and employment to fall. ABIn absence of further price shocks, prices wi
30、ll fall over time and economy moves back toward full employment.SRAS2CASE STUDY: The 1970s oil shocksACHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 25CASE STUDY: The 1970s oil shocksPredicted effects of the oil price shock: inflation output unemp
31、loyment and then a gradual recovery.奥肯法则油价的增长率而不是油价CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 26CASE STUDY: The 1970s oil shocksLate 1970s: As economy was recovering, oil prices shot up again, causing another huge supply shock!石油上涨主要是因为石油价格卡特尔
32、的形成CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 27CASE STUDY: The 1980s oil shocks1980s: A favorable supply shock-a significant fall in oil prices. As the model would predict, inflation and unemployment fell: CHAPTER 9CHAPTER 9 Introduction to E
33、conomic Fluctuations Introduction to Economic Fluctuationsslide 28Stabilization policydef: policy actions aimed at reducing the severity of short-run economic fluctuations.Example: Using monetary policy to combat the effects of adverse supply shocks:CHAPTER 9CHAPTER 9 Introduction to Economic Fluctu
34、ations Introduction to Economic Fluctuationsslide 29Stabilizing output with monetary policySRAS1Y PAD1BSRAS2AY2LRASThe adverse supply shock moves the economy to point B.CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 30Stabilizing output with monet
35、ary policyY PAD1BSRAS2ACY2LRASAD2But the Fed accommodates the shock by raising agg. demand.results: P is permanently higher, but Y remains at its full-employment level.CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 31Chapter summary1. Long run: pr
36、ices are flexible, output and employment are always at their natural rates, and the classical theory applies.Short run: prices are sticky, shocks can push output and employment away from their natural rates. 2. Aggregate demand and supply: a framework to analyze economic fluctuationsCHAPTER 9CHAPTER
37、 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 32Chapter summary3. The aggregate demand curve slopes downward.4. The long-run aggregate supply curve is vertical, because output depends on technology and factor supplies, but not prices.5. The short-run aggregate s
38、upply curve is horizontal, because prices are sticky at predetermined levels.CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 33Chapter summary6. Shocks to aggregate demand and supply cause fluctuations in GDP and employment in the short run.7. The Fed can attempt to stabilize the economy with monetary policy. CHAPTER 9CHAPTER 9 Introduction to Economic Fluctuations Introduction to Economic Fluctuationsslide 34
