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1、12 SHORT-RUN ECONOMIC FLUCTUATIONSCopyright 2004 South-Western33Aggregate Demand and Aggregate SupplyCopyright 2004 South-WesternShort-Run Economic Fluctuations Economic activity fluctuates from year to year. In most years production of goods and services rises. On average over the past 50 years, pr
2、oduction in the U.S. economy has grown by about 3 percent per year. In some years normal growth does not occur, causing a recession. Copyright 2004 South-WesternShort-Run Economic Fluctuations A recession is a period of declining real incomes, and rising unemployment. A depression is a severe recess
3、ion.Copyright 2004 South-WesternTHREE KEY FACTS ABOUT ECONOMIC FLUCTUATIONS Economic fluctuations are irregular and unpredictable. Fluctuations in the economy are often called the business cycle. Most macroeconomic variables fluctuate together. As output falls, unemployment rises.Figure 1 A Look At
4、Short-Run Economic FluctuationsBillions of 1996 DollarsReal GDP(a) Real GDP$10,0009,0008,0007,0006,0005,0004,0003,0002,000 19651970197519801985199019952000Copyright 2004 South-WesternCopyright 2004 South-WesternTHREE KEY FACTS ABOUT ECONOMIC FLUCTUATIONS Most macroeconomic variables fluctuate togeth
5、er. Most macroeconomic variables that measure some type of income or production fluctuate closely together. Although many macroeconomic variables fluctuate together, they fluctuate by different amounts.Figure 1 A Look At Short-Run Economic FluctuationsBillions of 1996 Dollars(b) Investment Spending$
6、1,8001,6001,4001,2001,000800600400200 19651970197519801985199019952000Investment spendingCopyright 2004 South-WesternCopyright 2004 South-WesternTHREE KEY FACTS ABOUT ECONOMIC FLUCTUATIONS As output falls, unemployment rises. Changes in real GDP are inversely related to changes in the unemployment r
7、ate. During times of recession, unemployment rises substantially.Figure 1 A Look At Short-Run Economic FluctuationsPercent of Labor Force(c) Unemployment Rate02468101219651970197519801985199019952000Unemployment rateCopyright 2004 South-WesternCopyright 2004 South-WesternEXPLAINING SHORT-RUN ECONOMI
8、C FLUCTUATIONS How the Short Run Differs from the Long Run Most economists believe that classical theory describes the world in the long run but not in the short run. Changes in the money supply affect nominal variables but not real variables in the long run. The assumption of monetary neutrality is
9、 not appropriate when studying year-to-year changes in the economy.Copyright 2004 South-WesternThe Basic Model of Economic Fluctuations Two variables are used to develop a model to analyze the short-run fluctuations. The economys output of goods and services measured by real GDP. The overall price l
10、evel measured by the CPI or the GDP deflator.Copyright 2004 South-WesternThe Basic Model of Economic Fluctuations The Basic Model of Aggregate Demand and Aggregate Supply Economist use the model of aggregate demand and aggregate supply to explain short-run fluctuations in economic activity around it
11、s long-run trend.Copyright 2004 South-WesternThe Basic Model of Economic Fluctuations The Basic Model of Aggregate Demand and Aggregate Supply The aggregate-demand curve shows the quantity of goods and services that households, firms, and the government want to buy at each price level.Copyright 2004
12、 South-WesternThe Basic Model of Economic Fluctuations The Basic Model of Aggregate Demand and Aggregate Supply The aggregate-supply curve shows the quantity of goods and services that firms choose to produce and sell at each price level.Figure 2 Aggregate Demand and Aggregate Supply.Quantity of Out
13、putPrice Level0Aggregate supplyAggregate demandEquilibrium outputEquilibrium price levelCopyright 2004 South-WesternCopyright 2004 South-WesternTHE AGGREGATE-DEMAND CURVE The four components of GDP (Y) contribute to the aggregate demand for goods and services. Y = C + I + G + NXFigure 3 The Aggregat
14、e-Demand Curve.Quantity of OutputPrice Level0Aggregate demandPYY2P21. A decrease in the price level . . .2. . . . increases the quantity of goods and services demanded.Copyright 2004 South-WesternCopyright 2004 South-WesternWhy the Aggregate-Demand Curve Is Downward Sloping The Price Level and Consu
15、mption: The Wealth Effect The Price Level and Investment: The Interest Rate Effect The Price Level and Net Exports: The Exchange-Rate EffectCopyright 2004 South-WesternWhy the Aggregate-Demand Curve Is Downward Sloping The Price Level and Consumption: The Wealth Effect A decrease in the price level
16、makes consumers feel more wealthy, which in turn encourages them to spend more. This increase in consumer spending means larger quantities of goods and services demanded.Copyright 2004 South-WesternWhy the Aggregate-Demand Curve Is Downward Sloping The Price Level and Investment: The Interest Rate Effect A
