1、1第三十三章总需求与总供给Aggregate Demand and Aggregate Supply2短期经济波动Short-Run Economic Fluctuations经济活动年复一年地波动Economic activity fluctuates from year to year.在大多数年份里，物品与服务的生产是上升的In most years production of goods and services rises.在过去50年，平均来说，美国经济的生产每年增长约3个百分点。On average over the past 50 years, production in th
2、e U.S. economy has grown by about 3 percent per year.在一些年份，正常的增长没能出现，导致了衰退。In some years normal growth does not occur, causing a recession.3短期经济波动Short-Run Economic Fluctuations衰退是实际GDP下降、收入减少、失业上升的时期A recession is a period of declining real GDP, falling incomes, and rising unemployment.萧条是严重的衰退A de
3、pression is a severe recession.4关于经济波动的三个关键事实Three Key Facts About Economic Fluctuations经济波动是不规则和不可预测的。Economic fluctuations are irregular and unpredictable.经济当中的波动常常被称作经济周期（或译商业周期）Fluctuations in the economy are often called the business cycle.大多数宏观经济变量一起波动。Most macroeconomic variables fluctuate to
4、gether.随着产出下降，失业率上升。As output falls, unemployment rises.5(a)Real GDP实际GDP短期经济波动一瞥A Look At Short-Run Economic FluctuationsBillions of2000 Dollars1965 1970 1975 1980 1985 1990 1995 2000 20052,0004,0006,0008,000$10,0003,0005,0007,0009,000Real GDP6衰退短期经济波动一瞥：中国A Look At Short-Run Economic Fluctuations:
5、 China(a)实际GDP资料来源：中国国内生产总值核算历史资料，19521995，中国统计年鉴以及作者计算。01000200030004000500060001952 1957 1962 1967 1972 1977 1982 1987 1992 1997 2002年 份指数（1952=100）27关于经济波动的三个关键事实Three Key Facts About Economic Fluctuations大多数宏观经济变量一起波动。Most macroeconomic variables fluctuate together.大多数衡量某种收入或生产的宏观经济变量几乎同时波动。Most
6、 macroeconomic variables that measure some type of income or production fluctuate closely together. 虽然许多宏观经济变量一起波动，他们波动的幅度并不同。Although many macroeconomic variables fluctuate together, they fluctuate by different amounts.8短期经济波动一瞥A Look At Short-Run Economic Fluctuations(b) Investment Spending投资支出196
7、5 1970 1975 1980 1985 1990 1995 2000 2005Billions of2000 Dollars05001,000$1,500InvestmentSpending9衰退短期经济波动一瞥：中国A Look At Short-Run Economic Fluctuations: China(b) 投资支出0200040006000800010000120001952 1957 1962 1967 1972 1977 1982 1987 1992 1997 2002年 份指数（1952=100）10中国：GDP、工业生产总值、固定资产投资年增长率的波动-20%-10%
8、0%10%20%30%40%50%60%70%1978 1983 1988 1993 1998 2003GDP增长率工业总产值增长率固定资产投资增长率资料来源：新中国五十年统计资料汇编统计年鉴11关于经济波动的三个关键事实Three Key Facts About Economic Fluctuations随着产出下降，失业上升。As output falls, unemployment rises.实际GDP的变化和失业率的变化呈反向关系。Changes in real GDP are inversely related to changes in the unemployment rate
9、.在衰退时期，失业大幅上升。During times of recession, unemployment rises substantially.12短期经济波动一瞥A Look At Short-Run Economic Fluctuations(c) Unemployment Rate失业率1965 1970 1975 1980 1985 1990 1995 2000 2005Percent ofLabor Force24681012%UnemploymentRate313解释短期经济波动Explaining Short-run Economic Fluctuations古典经济学的基本
10、假设是古典二分法与货币货币中性。The basic assumptions of classical economics are the classical dichotomy and monetary neutrality.所有宏观变量分成两类：名义变量与实际变量。All macroeconomic variables can be separated into two groups: nominal variables and real variables.货币供给的变化影响名义变量而非实际变量。Changes in the money supply affect nominal vari
11、ables but not real variables.14解释短期经济波动Explaining Short-run Economic Fluctuations按照古典经济学，我们在不引入名义变量（货币供给、价格水平）的情况下，就能够考察实际变量（实际GDP、实际利率和失业）的决定。According to classical economics, we are able to examine the determinants of real variables (real GDP, the real interest rate, and unemployment) without intr
12、oducing nominal variables (the money supply and the price level.)大多数经济学家相信，古典理论描述了长期中的世界，但没有描述短期中的世界。Most economists believe that classical theory describes the world in the long run but not in the short run.15解释短期经济波动Explaining Short-run Economic Fluctuations短期内，实际和名义变量高度相关。In the short run, real a
13、nd nominal variables are highly intertwined.货币供给的变化能够暂时地将实际GDP移到其长期趋势之外。Changes in the money supply can temporarily push real GDP away from its long-run trend.一个旨在解释短期经济的新模型需要集中关注名义和实际变量的相互影响。A new model aiming to explain the economy in the short-run should focus on how real and nominal variables in
14、teract.16总需求与总供给模型The Model of Aggregate Demand and Aggregate Supply短期经济波动模型集中关注两个变量的行为。The model of short-run economic fluctuation focuses on the behavior of two variables.（以实际GDP衡量的）经济中物品与服务的产出。The economys output of goods and services measured by real GDP.（以CPI或GDP平减指数衡量的）整体价格水平。The overall price
15、 level measured by the CPI or the GDP deflator.总需求与总供给模型The Model of Aggregate Demand and Aggregate Supply经济学家使用总需求与总供给模型来解释经济活动围绕其长期趋势的短期波动Economist use the model of aggregate demand and aggregate supply to explain short-run fluctuations in economic activity around its long-run trend.18总需求与总供给Aggre
16、gate Demand and Aggregate Supply.EquilibriumOutput均衡产出Quantity ofOutput产出数量PriceLevel价格水平0Equilibriumprice level均衡价格水平AggregateSupply总供给AggregateDemand总需求419总需求与总供给模型The Model of Aggregate Demand and Aggregate Supply总需求曲线表示家庭、企业或政府在任一价格水平上想要购买的物品与服务的数量。The aggregate demand curve shows the quantity o
17、f goods and services that households, firms, and the government want to buy at each price level.不是单个物品市场需求曲线的加总。It is not the sum of the market demand curves for individual goods.20总需求与总供给模型The Model of Aggregate Demand and Aggregate Supply总供给曲线表示企业在任一价格水平上生产和销售的物品与服务的数量。The aggregate supply curve s
18、hows the quantity of goods and services that firms produce and sell at each price level.不是单个物品市场供给曲线的加总。It is not the sum of the market supply curves of individual goods.21总需求曲线The Aggregate Demand CurveGDP（总支出）的四个组成部分即构成了对物品与服务的总需求。The four components of GDP (total expenditure) contribute to the ag
19、gregate demand for goods and services.AD C + I + G + NX22总需求曲线The Aggregate-Demand Curve.Quantity ofOutputPriceLevel0AggregateDemand总需求P1Y1Y2P22. 增加了物品与服务的需求数量increases the quantity of goods and services demanded.1. 价格水平的下降A decrease in the price level.23为什么总需求曲线向下倾斜Why the Aggregate Demand Curve Is
20、 Downward Sloping价格水平与消费：财富效应The Price Level and Consumption: The Wealth Effect价格水平与投资：利率效应The Price Level and Investment: The Interest Rate Effect价格水平与净出口：汇率效应The Price Level and Net Exports: The Exchange-Rate Effect24价格水平与消费：财富效应The Price Level and Consumption: The Wealth Effect价格水平的下降使得消费者感觉更加富有，
21、这反过来鼓励他们支出更多。A decrease in the price level makes consumers feel more wealthy, which in turn encourages them to spend more. 消费支出的上升意味着对物品与服务更大的需求数量。This increase in consumer spending means larger quantities of goods and services demanded.525价格水平与投资：利率效应The Price Level and Investment: The Interest Rat
22、e Effect更低的价格水平降低了利率，这鼓励了对投资品的更大支出。A lower price level reduces the interest rate, which encourages greater spending on investment goods.投资支出的增加意味着物品与服务的需求数量更大。This increase in investment spending means a larger quantity of goods and services demanded.26价格水平与净出口：汇率效应The Price Level and net Exports: T
23、he Exchange-Rate Effect当美国的价格水平下降导致了美国的利率下降，实际汇率就会贬值，这又刺激了美国的净出口。When a fall in the U.S. price level causes U.S. interest rates to fall, the real exchange rate depreciates, which stimulates U.S. net exports.净出口支出的增加意味着物品与服务的需求数量更大。The increase in net export spending means a larger quantity of goods
24、and services demanded.27总需求曲线为什么会移动Why the Aggregate Demand Curve Might Shift总需求曲线向下倾斜，表示价格水平的下降增加了物品与服务总的需求数量。The downward slope of the aggregate demand curve shows that a fall in the price level raises the overall quantity of goods and services demanded.然而，在给定价格水平上，许多其他因素影响物品与服务的需求数量。Many other fa
25、ctors, however, affect the quantity of goods and services demanded at any given price level. 当这些其他因素中的任一种发生改变，总需求曲线移动。When one of these other factors changes, the aggregate demand curve shifts.28总需求曲线为什么会移动Why the Aggregate Demand Curve Might Shift来自消费的移动Shifts arising from Consumption来自投资的移动Shifts
26、arising from Investment来自政府购买的移动Shifts arising from Government Purchases来自净出口的移动Shifts arising from Net Exports29总需求曲线的移动Shifts in the Aggregate Demand Curve.Quantity ofOutputPriceLevel0Aggregatedemand, D1P1Y1D2Y2 30总供给曲线The Aggregate Supply Curve在长期中，总供给曲线是垂直的。In the long run, the aggregate-supply
27、curve is vertical.在短期内，总供给曲线向上倾斜。In the short run, the aggregate-supply curve is upward sloping.631长期总供给曲线The Long-Run Aggregate Supply Curve垂直的长期总供给曲线是古典理论的图形表示。The vertical long-run aggregate-supply curve is a graphical representation of the classical theory.在长期中，经济的物品与服务的生产依赖于它的劳动、资本与自然资源的供给，以及将这
28、些生产要素转化为产品与服务的可行技术。In the long-run, an economys production of goods and services depends on its supplies of labor, capital, and natural resources and on the available technology used to turn these factors of production into goods and services. 价格水平在长期中不影响这些变量。The price level does not affect these va
29、riables in the long run.32长期总供给曲线The Long-Run Aggregate- Supply Curve.Quantity ofOutputNatural rateof output自然产量率Price Level0Long-runaggregatesupply长期总供给P1P2 2. 不影响长期中物品与服务的供给数量does not affect the quantity of goods and services supplied in the long run.1. 价格水平的改变A change in the price level33长期总供给曲线T
30、he Long-Run Aggregate Supply Curve长期总供给曲线垂直于自然产出率处。The long-run aggregate supply curve is vertical at the natural rate of output.这一生产水平也被称为潜在产出或充分就业产出。This level of production is also referred to as potential output or full-employment output.34长期总供给曲线为什么会移动Why the Long-Run Aggregate Supply Curve Mig
31、ht Shift任何改变自然产出率的经济变化都会移动长期总供给曲线。Any change in the economy that alters the natural rate of output shifts the long-run aggregate-supply curve.这样的移动可以按照古典模型中影响产出的若干因素来分类。The shifts may be categorized according to the various factors in the classical model that affect output.35长期总供给曲线为什么移动Why the Long
32、-Run Aggregate Supply Curve Might Shift来自劳动的移动Shifts arising from Labor来自资本的移动Shifts arising from Capital来自自然资源的移动Shifts arising from Natural Resources来自技术知识的移动Shifts arising from Technological Knowledge361. 在长期中，技术进步移动长期总供给In the long-run, technological progress shifts long-run aggregate supply.LRA
33、S2000LRAS1990Quantity ofOutputPrice Level0P1980Y1980AD1980P2000P1990LRAS19802. 货币供给的增长移动总需求and growth in the money supply shifts aggregate-demand.AD2000AD19904. 和持续的通货膨胀and ongoing inflation.Y1990Y20003. 导致产出增长leading to growth in output.运用总供求模型描述长期增长与通货膨胀Using Aggregate Demand and Aggregate Supply
34、to Depict Long-Run Growth and Inflation.737运用总供求模型描述长期增长与通货膨胀Using Aggregate Demand and Aggregate Supply to Depict Long-Run Growth and Inflation长期来讲，产出的变动（增长）只取决于长期供给曲线的移动，和关于长期中实际经济的古典理论完全一致。长期来讲，价格水平的变动（通胀）可以来自于：总需求的变动，这包含但不限于货币供给的变动长期总供给的变动这扩展了关于长期中货币与物价的古典理论。38短期总供给曲线为什么向上倾斜Why the Short-Run Agg
35、regate Supply Curve Slopes Upward in the Short Run在短期内，经济中整体价格水平的上升倾向于增加物品与服务的供给数量。In the short run, an increase in the overall level of prices in the economy tends to raise the quantity of goods and services supplied.价格水平的下降倾向于减少物品与服务的供给数量。A decrease in the level of prices tends to reduce the quant
36、ity of goods and services supplied.39短期总供给曲线The Short-Run Aggregate Supply Curve.Quantity ofOutputPrice Level0Short-runaggregatesupply短期总供给Y1P1Y22. 减少了短期内物品与服务的供给数量reduces the quantity of goods and services supplied in the short run.P21. 价格水平的下降A decrease in the price level40短期总供给曲线为什么向上倾斜Why the Sh
37、ort-Run Aggregate Supply Curve Slopes Upward in the Short Run粘性工资理论The Sticky-Wage Theory粘性价格理论The Sticky-Price Theory错觉理论The Misperceptions Theory41粘性工资理论The Sticky-Wage Theory名义工资的调整是缓慢的，或者说，在短期内是“粘性的”工资并不随着价格水平的下降而立即调整。Nominal wages are slow to adjust, or are “sticky”in the short run: Wages do no
38、t adjust immediately to a fall in the price level.更低的价格水平使得雇佣和生产的利润更低。A lower price level makes employment and production less profitable.这就导致企业减少物品与服务的供给数量。This induces firms to reduce the quantity of goods and services supplied.42粘性价格理论The Sticky-Price Theory某些物品与服务的价格为适应经济状况变化所进行的调整是迟缓的。Prices of
39、 some goods and services adjust sluggishly in response to changing economic conditions: 价格水平的未预料到的下降，留下某些企业的价格超过了合意的水平。An unexpected fall in the price level leaves some firms with higher-than-desired prices.这会压低销售，引起企业减少物品与服务的生产数量。This depresses sales, which induces firms to reduce the quantity of g
40、oods and services they produce.843错觉理论The Misperceptions Theory总体价格水平的改变，暂时地误导供给者，让他们在出售自己产出的市场上，看不清正在发生什么。Changes in the overall price level temporarily mislead suppliers about what is happening in the markets in which they sell their output:更低的价格水平导致了对相对价格的错觉。A lower price level causes mispercepti
41、ons about relative prices.这种错觉使得供给者减少物品与服务的供给数量。These misperceptions induce suppliers to decrease the quantity of goods and services supplied.44短期总供给曲线为什么向上倾斜Why the Short-Run Aggregate Supply Curve Slopes Upward in the Short Run所有三个理论都表明，当实际价格水平背离人们预期的价格水平时，产量就背离其自然率。All the three theories suggest
42、that output deviates from its natural rate when the price level deviates from the price level that people expect.当实际价格水平高于人们预期的水平时，产量就高于其自然率。When the price rises above the level that people expected, output rises above its natural rate.45短期总供给曲线为什么向上倾斜Why the Short-Run Aggregate Supply Curve Slopes
43、Upward in the Short Run供给者自己的产品价格上升其他供给者的价格上升供给者的产品价格上升当实际价格上升而高于预期时供给者自己产品的相对价格下降，需求上升，从而增加产出。供给者自己产品的价格难以调整粘性价格理论供给者误认为自己产品的相对价格上升，从而增加产出供给者认为其他产品价格不变错觉理论供给者由于实际工资下降而增加产出供给者难以调整名义工资粘性工资理论结果是产出增加在短期内，预期价格不变46短期总供给曲线为什么向上倾斜Why the Short-Run Aggregate Supply Curve Slopes Upward in the Short Run用数学公式将
44、产品供给量、实际和预期价格水平的关系表述如下: We can express this mathematically as follows：产品供给量自然产量率a(实际价格水平预期价格水平) Quantity of output supplied = Natural rate of output + a (Actual price level Expected price level)这里的a是决定产出对价格的未预期改变的反映程度。Where a is a number that determines how much output responds to unexpected changes
45、 in the price level.47短期总供给曲线为什么向上倾斜Why the Short-Run Aggregate Supply Curve Slopes Upward in the Short Run上述公式同时包含了短期和长期的总供给曲线：短期中，预期价格水平不变，实际价格水平的上升增加了产品供给量，总供给曲线向上倾斜。长期中，预期价格水平与实际价格水平相等，总供给曲线垂直于自然产量率处。48总供给曲线为什么会移动Why the Aggregate Supply Curve Might Shift来自劳动力的移动Shifts arising from Labor来自资本的移动S
46、hifts arising from Capital来自自然资源的移动Shifts arising from Natural Resources.来自技术的移动Shifts arising from Technology.来自预期价格水平的移动Shifts arising from the Expected Price Level.949预期价格水平的上升减少了物品与服务的供给数量，将短期总供给曲线向左移动。An increase in the expected price level reduces the quantity of goods and services supplied an
47、d shifts the short-run aggregate supply curve to the left.预期价格水平的下降增加了物品与服务的供给数量，将短期总供给曲线向右移动。A decrease in the expected price level raises the quantity of goods and services supplied and shifts the short-run aggregate supply curve to the right.总供给曲线为什么会移动Why the Aggregate Supply Curve Might Shift50
48、总供给曲线为什么会移动Why the Aggregate Supply Curve Might Shift预期对短期总供给曲线位置的影响在解释经济如何从短期转向长期时起了关键作用。The influence of expectations on the position of the short-run aggregate-supply curve plays a key role in explaining how the economy makes the transition from the short run to the long run.在短期中，预期是固定的，经济处于总需求与短
49、期总供给曲线的交点。In the short run, expectations are fixed, and the economy finds itself at the intersection of the aggregate-demand curve and the short-run aggregate-supply curve.在长期中，人们的预期可以调整，短期总供给曲线将移动。In the long run, peoples expectations adjust, and the short-run aggregate-supply curve shifts.这种移动保证了经济最终会处于总需求曲线与长期总供给曲线的交点。T
