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1、Learning objectives,This chapter introduces you to (1)the issues that macroeconomists study; (2)the tools that macroeconomists use; (3) some important concepts in macroeconomic analysis,宏观经济学家研究的问题；使用的工具；宏观经济分析中的一些重要概念,Important issues in macroeconomics,Why are millions of people unemployed, even wh
2、en the economy is booming? Why are there recessions? Can the government do anything to combat recessions? Should it?,为何即使经济高涨的时候，也有大量劳动力失业？ 为什么有衰退？政府能做什么？该不该做？,Important issues in macroeconomics,What is the government budget deficit? How does it affect the economy? Why does the U.S. have such a huge
3、 trade deficit? Why are so many countries poor? What policies might help them grow out of poverty?,什么是政府预算赤字（budget deficit）？美国为什么有巨额赤字？ 为什么那么多的国家贫穷？什么样的政策可以帮助他们摆脱贫困？,U.S. Gross Domestic Product in billions of chained 1996 dollars,GDP,U.S. Gross Domestic Product in billions of chained 1996 dollars,最
4、长的经济扩张记录,衰退,Why learn macroeconomics? 为什么学习宏观经济学？,The macroeconomy affects societys well-being（社会福利）. example: Unemployment and social problems,Each one-point increase in the u-rate（失业率） is associated with: 920 more suicides（自杀者） 650 more homicides（杀人者） 4000 more people admitted to state mental inst
5、itutions 3300 more people sent to state prisons（监狱） 37, 000 more deaths（死亡） increases in domestic violence and homelessness（无家）可归）,例如：失业和社会问题,Why learn macroeconomics?,The macroeconomy affects your well-being. Unemployment and earnings growth,每小时工资增长率,失业率,Why learn macroeconomics?,The macroeconomy a
6、ffects your well-being. Interest rates and mortgage payments,For a $150,000 30-year mortgage（抵押）:,$9,888,$824,5.21%,$11,520,$960,6.63%,6/20/03,Why learn macroeconomics?,The macroeconomy affects politics & current events. Inflation and unemployment in election years,year U rate inflation rate elec. o
7、utcome 1976 7.7% 5.8% Carter (D) 1980 7.1% 13.5% Reagan (R) 1984 7.5% 4.3% Reagan (R) 1988 5.5% 4.1% Bush I (R) 1992 7.5% 3.0% Clinton (D) 1996 5.4% 3.3% Clinton (D) 2000 4.0% 3.4% Bush II (R),Economic models（经济模型）,are simplified versions of a more complex reality irrelevant details are stripped awa
8、y Used to （1）show the relationships between economic variables （2）explain the economys behavior （3）devise policies to improve economic performance,不相干的细节都被剥离掉了,是对真实世界的简化,Example of a model: The supply & demand for new cars,explains the factors that determine the price of cars and the quantity sold a
9、ssumes the market is competitive: each buyer and seller is too small to affect the market price Variables: Q d = quantity of cars that buyers demand Q s = quantity that producers supply P = price of new cars Y = aggregate income（外生变量） Ps = price of steel (an input) （外生变量）,The demand for cars,shows t
10、hat the quantity of cars consumers demand is related to the price of cars and aggregate income.,Digression: Functional notation,General functional notation shows only that the variables are related:,Digression: Functional notation,General functional notation shows only that the variables are related
11、:,A specific functional form shows the precise quantitative relationship:,The market for cars: demand,Q Quantity of cars,P Price of cars,The demand curve shows the relationship between quantity demanded and price, other things equal.,The market for cars: supply,The market for cars: equilibrium,The e
12、ffects of an increase in income:,An increase in income increases the quantity of cars consumers demand at each price.,which increases the equilibrium price and quantity.,The effects of a steel price increase:,An increase in Ps reduces the quantity of cars producers supply at each price,which increas
13、es the market price and reduces the quantity.,Ps = price of steel (an input),Endogenous vs. exogenous variables:,The values of endogenous variables are determined in the model. The values of exogenous variables are determined outside the model: the model takes their values & behavior as given. In th
14、e model of supply & demand for cars,内生变量对外生变量,外生的,Y = aggregate income,Ps = price of steel (an input),Now you try:,Write down demand and supply equations for wireless phones; include two exogenous variables in each equation. Draw a supply-demand graph for wireless phones. Use your graph to show how
15、a change in one of your exogenous variables affects the models endogenous variables.,A multitude of models,No one model can address all the issues we care about. For example, If we want to know how a fall in aggregate income affects new car prices, we can use the S/D model（供需模型） for new cars. But if
16、 we want to know why aggregate income falls, we need a different model.,没有一个模型是万能的，不同问题需要不同模型。,A Multitude of Models,So we will learn different models for studying different issues (e.g., unemployment, inflation, long-run growth). For each new model, you should keep track of its assumptions（它的假定） , which of its variables are endogenous and which are exogenous（变量内生还是外生）, the questions it can help us understand, and those it cannot.,Prices: flexible versus sticky,Market cleari
