《宏观经济学》课程教学资源（英文版）Lecture1- 2 Intro 2 The Data of Macroeconomics

Worth: Mankiw Economics 5e CHAPTER TW O The Data of macroeconomics It is a capital mistake to theorize before one has data Insensibly one begins to twist facts to suit theories, instead of theories to fit facts. Sherlock holmes Scientists, economists, and detectives have much in common: they all want to figure out what's going on in the world around them. To do this, they rely on both theory and observation. They build theories in an attempt to make sense of what they see happening. They then turn to more systematic observation to eval- uate the theories validity. Only when theory and evidence come into line do they feel they understand the situation. This chapter discusses the types of obser vation that economists use to develop and test their theories Casual observation is one source of information about what's happening in the economy. When you go shopping, you see how fast prices are rising. When you look for a job, you learn whether firms are hiring. Because we are all partic ipants in the economy, we get some sense of economic conditions as we go bout our lives A century ago, economists monitoring the economy had little more to go on than these casual observations. Such fragmentary information made economic policymaking all the more difficult. One persons anecdote would suggest the economy was moving in one direction, while a different persons anecdote would suggest it was moving in another. Economists needed some way to com- bine many individual experiences into a coherent whole. There was an obvious solution: as the old quip goes, the plural of"" is"data Today, economic data offer a systematic and objective source of information and almost every day the newspaper has a story about some newly released statis- tic. Most of these statistics are produced by the government. Various government agencies survey households and firms to learn about their economic activity- how much they are earning, what they are buying, what prices they are charging, whether they have a job or are looking for work, and so on. From ese sur various statistics are computed that summarize the state of the economy. Econo- mists use these statistics to study the economy; policymakers use them to moni- tor developments and formulate policies This chapter focuses on the three statistics that economists and policymakers use most often. Gross domestic product, or GDP, tells us the nations total income User JOENA: Job EFF01418: 6264_ch02: Pg 15: 24933 #/eps at 1004 I Tue,Feb12,20028:404M

User JOEWA:Job EFF01418:6264_ch02:Pg 15:24933#/eps at 100% *24933* Tue, Feb 12, 2002 8:40 AM Scientists, economists, and detectives have much in common: they all want to figure out what’s going on in the world around them.To do this, they rely on both theory and observation.They build theories in an attempt to make sense of what they see happening.They then turn to more systematic observation to eval￾uate the theories’ validity. Only when theory and evidence come into line do they feel they understand the situation.This chapter discusses the types of obser￾vation that economists use to develop and test their theories. Casual observation is one source of information about what’s happening in the economy.When you go shopping, you see how fast prices are rising.When you look for a job, you learn whether firms are hiring. Because we are all partic￾ipants in the economy, we get some sense of economic conditions as we go about our lives. A century ago, economists monitoring the economy had little more to go on than these casual observations. Such fragmentary information made economic policymaking all the more difficult. One person’s anecdote would suggest the economy was moving in one direction, while a different person’s anecdote would suggest it was moving in another. Economists needed some way to com￾bine many individual experiences into a coherent whole.There was an obvious solution: as the old quip goes, the plural of “anecdote” is “data.” Today, economic data offer a systematic and objective source of information, and almost every day the newspaper has a story about some newly released statis￾tic. Most of these statistics are produced by the government.Various government agencies survey households and firms to learn about their economic activity— how much they are earning, what they are buying, what prices they are charging, whether they have a job or are looking for work, and so on. From these surveys, various statistics are computed that summarize the state of the economy. Econo￾mists use these statistics to study the economy; policymakers use them to moni￾tor developments and formulate policies. This chapter focuses on the three statistics that economists and policymakers use most often. Gross domestic product, or GDP, tells us the nation’s total income | 15 The Data of Macroeconomics 2CHAPTER It is a capital mistake to theorize before one has data.Insensibly one begins to twist facts to suit theories, instead of theories to fit facts. — Sherlock Holmes TWO

Worth: Mankiw Economics 5e and the total expenditure on its output of goods and services. The consumer price index, or CPl, measures the level of prices. The unemployment rate tells us the fraction of workers who are unemployed. In the following pages, we see how these statistics are computed and what they tell us about the econom 2-1 Measuring the Value of Economic Activity: Gross domestic product Gross domestic product is often considered the best measure of how well the economy is performing. This statistic is computed every three months by the bu- reau of Economic Analysis(a part of the U.S. Department of Commerce) from a large number of primary data sources. The goal of GDP is to summarize in a sin- gle number the dollar value of economic activity in a given period of time. There are two ways to view this statistic. One way to view gDp is as the total income of everyone in the economy. Another way to view GDP is as the total expendi ture on the econommy's output of goods and services. From either viewpoint, it is clear why GDP is a gauge of economic performance. GDP measures something peo- ple care about--their incomes Similarly, an economy with a large output of pods and services can better satisfy the demands of households, firms, and the government. How can GDP measure both the economy's income and the expenditure on its output? The reason is that these two quantities are really the same: for the economy as a whole, income must equal expenditure. That fact, in turn, follows from an even more fundamental one: because every transaction has both a buyer and a seller, every dollar of expenditure by a buyer must become a dollar of in come to a seller. When Joe paints Jane's house for $1, 000, that $1,000 is income to Joe and expenditure by Jane. The transaction contributes $1,000 to GDP, re- gardless of whether we are adding up all income or adding up all expenditure To understand the meaning of GDP more fully, we turn to national income accounting, the accounting system used to measure GDP and many related statistics Income, Expenditure, and the Circular Flow Imagine an economy that produces a single good, bread, from a single input, labor. Figure 2-1 illustrates all the economic transactions that occur between households and firms in this economy. The inner loop in Figure 2-1 represents the flows of bread and labor. The households sell their labor to the firms The firms use the labor of their workers to produce bread, which the firms in turn sell to the households. Hence, labor flows from households to firms and bread fows from firms to households. The outer loop in Figure 2-1 represents the corresponding flow of dollars The households buy bread from the firms. The firms use some of the revenue User JoENA: Job EFFo1418: 6264_ch02: Pg 16: 24934#/eps at 1004 mI Tue,Feb12,20028:404M

User JOEWA:Job EFF01418:6264_ch02:Pg 16:24934#/eps at 100% *24934* Tue, Feb 12, 2002 8:40 AM and the total expenditure on its output of goods and services. The consumer price index, or CPI, measures the level of prices.The unemployment rate tells us the fraction of workers who are unemployed. In the following pages, we see how these statistics are computed and what they tell us about the economy. 2-1 Measuring the Value of Economic Activity: Gross Domestic Product Gross domestic product is often considered the best measure of how well the economy is performing.This statistic is computed every three months by the Bu￾reau of Economic Analysis (a part of the U.S. Department of Commerce) from a large number of primary data sources.The goal of GDP is to summarize in a sin￾gle number the dollar value of economic activity in a given period of time. There are two ways to view this statistic. One way to view GDP is as the total income of everyone in the economy.Another way to view GDP is as the total expendi￾ture on the economy’s output of goods and services. From either viewpoint, it is clear why GDP is a gauge of economic performance. GDP measures something peo￾ple care about—their incomes. Similarly, an economy with a large output of goods and services can better satisfy the demands of households, firms, and the government. How can GDP measure both the economy’s income and the expenditure on its output? The reason is that these two quantities are really the same: for the economy as a whole, income must equal expenditure.That fact, in turn, follows from an even more fundamental one: because every transaction has both a buyer and a seller, every dollar of expenditure by a buyer must become a dollar of in￾come to a seller.When Joe paints Jane’s house for $1,000, that $1,000 is income to Joe and expenditure by Jane.The transaction contributes $1,000 to GDP, re￾gardless of whether we are adding up all income or adding up all expenditure. To understand the meaning of GDP more fully, we turn to national income accounting, the accounting system used to measure GDP and many related statistics. Income, Expenditure, and the Circular Flow Imagine an economy that produces a single good, bread, from a single input, labor. Figure 2-1 illustrates all the economic transactions that occur between households and firms in this economy. The inner loop in Figure 2-1 represents the flows of bread and labor. The households sell their labor to the firms.The firms use the labor of their workers to produce bread, which the firms in turn sell to the households. Hence, labor flows from households to firms, and bread flows from firms to households. The outer loop in Figure 2-1 represents the corresponding flow of dollars. The households buy bread from the firms.The firms use some of the revenue 16 | PART I Introduction

Worth: Mankiw Economics 5e 2 The data of 117 g he Circular Flow This Income(S) figure illustrates the flows between firms and households nomy that produces good, bread, fre inner loop represent the flows of labor and bread. households sell their labor to firms and the firms sell the bread Household they produce to loop represents the corresponding flows of dollars: households pay the firms for the bread and the firms pay wages Goods(bread Expenditure(S economy, GDP is both the total expenditure bread and the total income from the production of bread from these sales to pay the wages of their workers, and the remainder is the profit belonging to the owners of the firms(who themselves are part of the household sector). Hence, expenditure on bread flows from households to firms, and in- come in the form of wages and profit flows from firms to households GDP measures the How of dollars in this economy. We can compute it in two ays. GDP is the total income from the production of bread, which equals the sum of wages and profit-the top half of the circular flow of dollars. GDP is also the total expenditure on purchases of bread--the bottom half of the circular How of dollars. To compute GDP, we can look at either the flow of dollars from firms to households or the fow of dollars from households to firms These two ways of computing GDP must be equal because the expenditure of buyers on products is, by the rules of accounting, income to the sellers of those products. Every transaction that affects expenditure must affect income, and every transaction that affects income must affect expenditure. For example, suppose that a firm produces and sells one more loaf of bread to a household Clearly this transaction raises total expenditure on bread, but it also has an equal effect on total income. If the firm produces the extra loaf without hiring any more labor(such as by making the production process more efficient), then profit increases. If the firm produces the extra loaf by hiring more labor, then wages increase In both cases, expenditure and income increase equally User JOENA: Job EFF01418: 6264_ch02: Pg 17:24935#/eps at 1004 IlmI Tue,Feb12,20028:404M

User JOEWA:Job EFF01418:6264_ch02:Pg 17:24935#/eps at 100% *24935* Tue, Feb 12, 2002 8:40 AM from these sales to pay the wages of their workers, and the remainder is the profit belonging to the owners of the firms (who themselves are part of the household sector). Hence, expenditure on bread flows from households to firms, and in￾come in the form of wages and profit flows from firms to households. GDP measures the flow of dollars in this economy. We can compute it in two ways. GDP is the total income from the production of bread, which equals the sum of wages and profit—the top half of the circular flow of dollars. GDP is also the total expenditure on purchases of bread—the bottom half of the circular flow of dollars.To compute GDP, we can look at either the flow of dollars from firms to households or the flow of dollars from households to firms. These two ways of computing GDP must be equal because the expenditure of buyers on products is, by the rules of accounting, income to the sellers of those products. Every transaction that affects expenditure must affect income, and every transaction that affects income must affect expenditure. For example, suppose that a firm produces and sells one more loaf of bread to a household. Clearly this transaction raises total expenditure on bread, but it also has an equal effect on total income. If the firm produces the extra loaf without hiring any more labor (such as by making the production process more efficient), then profit increases. If the firm produces the extra loaf by hiring more labor, then wages increase. In both cases, expenditure and income increase equally. CHAPTER 2 The Data of Macroeconomics | 17 figure 2-1 Income ($) Labor Goods (bread ) Expenditure ($) Households Firms The Circular Flow This figure illustrates the flows between firms and households in an economy that produces one good, bread, from one input, labor. The inner loop represents the flows of labor and bread: households sell their labor to firms, and the firms sell the bread they produce to households. The outer loop represents the corresponding flows of dollars: households pay the firms for the bread, and the firms pay wages and profit to the households. In this economy, GDP is both the total expenditure on bread and the total income from the production of bread

Worth: Mankiw Economics 5e 18 PART IIntroduction Stocks and flows Many economic variables measure a quantity of! understand that this means that it is $10 trillion something-a quantity of money, a quantity ofi per year .(Equivalently, we could say that U.S GDP is $317,000 per second. tween two types of quantity variables: stocks and Stocks and flows are often related. In the point in time, whereas a flow is a quantity mea-i The stock of water in the tub represents the accu- sured per unit of time mulation of the flow out of the faucet. and the The bathtub, shown in Figure 2-2, is the clas- flow of water represents the change in the stock. sic example used to illustrate stocks and flows.i When building theories to explain economic vari- The amount of water in the tub is a stock: it is the ables it is often useful to determine whether the uantity of water in the tub at a given point in i variables are stocks or flows and whether any re- time. The amount of water coming out of the i lationships link them faucet is a flow: it is the quantity of water being Here are some examples of related stocks and dded to the tub per unit of time. Note that wei flows that we study in future chapters measure stocks and flows in different units. Wei> A person's wealth is a stock; income and ex- say that the bathtub contains 50 gallons of water, but that water is coming out of the faucet at 5 penditure are flows The number of unemployed people is a stock; GDP is probably the most important flow the number of people losing their jobs is a flow. variable in economics: it tells us how many dol-i The amount of capital in the economy is a lars are flowing around the economy's circular stock; the e amount flow per unit of time. When you hear someone> The government debt is a stock; the govern say that the U.S. GDP is $10 trillion, you should ment budget deficit is a flow. figure 2-2 Stock Stocks and Flows The amount of water in a bathtub is a stock. it is a quantity measured at a given moment in time. The amount of water coming out of the faucet is a flow per unit of time Rules for Computing GDP In an economy that produces only bread, we can compute gDP by adding up the total expenditure on bread. Real economies, however, include the produc- tion and sale of a vast number of goods and services. To compute GDP for such a complex economy, it will be helpful to have a more precise definition: gre User JOENA: Job EFF01418: 6264_ch02: Pg 18: 24936 #/eps at 1004 II Tue,Feb12,20028:404M

User JOEWA:Job EFF01418:6264_ch02:Pg 18:24936#/eps at 100% *24936* Tue, Feb 12, 2002 8:40 AM Rules for Computing GDP In an economy that produces only bread, we can compute GDP by adding up the total expenditure on bread. Real economies, however, include the produc￾tion and sale of a vast number of goods and services.To compute GDP for such a complex economy, it will be helpful to have a more precise definition: gross 18 | PART I Introduction FYI Many economic variables measure a quantity of something—a quantity of money, a quantity of goods, and so on. Economists distinguish be￾tween two types of quantity variables: stocks and flows. A stock is a quantity measured at a given point in time, whereas a flow is a quantity mea￾sured per unit of time. The bathtub, shown in Figure 2-2, is the clas￾sic example used to illustrate stocks and flows. The amount of water in the tub is a stock: it is the quantity of water in the tub at a given point in time. The amount of water coming out of the faucet is a flow: it is the quantity of water being added to the tub per unit of time. Note that we measure stocks and flows in different units. We say that the bathtub contains 50 gallons of water, but that water is coming out of the faucet at 5 gallons per minute. GDP is probably the most important flow variable in economics: it tells us how many dol￾lars are flowing around the economy’s circular flow per unit of time. When you hear someone say that the U.S. GDP is $10 trillion, you should Stocks and Flows understand that this means that it is $10 trillion per year. (Equivalently, we could say that U.S. GDP is $317,000 per second.) Stocks and flows are often related. In the bathtub example, these relationships are clear. The stock of water in the tub represents the accu￾mulation of the flow out of the faucet, and the flow of water represents the change in the stock. When building theories to explain economic vari￾ables, it is often useful to determine whether the variables are stocks or flows and whether any re￾lationships link them. Here are some examples of related stocks and flows that we study in future chapters: ➤ A person’s wealth is a stock; income and ex￾penditure are flows. ➤ The number of unemployed people is a stock; the number of people losing their jobs is a flow. ➤ The amount of capital in the economy is a stock; the amount of investment is a flow. ➤ The government debt is a stock; the govern￾ment budget deficit is a flow. figure 2-2 Flow Stock Stocks and Flows The amount of water in a bathtub is a stock: it is a quantity measured at a given moment in time. The amount of water coming out of the faucet is a flow: it is a quantity measured per unit of time

Worth: Mankiw Ecol 2 The Data of macroeco domestic product(GDP) is the market value of all final goods and services produced within an economy in a given period of time. To see how this definition is applied, let's dis- cuss some of the rules that economists follow in constructing this statistic Adding Apples and Oranges The U.S. economy produces many different goods and services--hamburgers, haircuts, cars, computers, and so on GDP combines the value of these goods and services into a single measure. The diver- sity of products in the economy complicates the calculation of GDP because different products have different values Suppose, for example, that the economy produces four apples and three oranges How do we compute GDP? We could simply add apples and oranges and conclude that GDP equals seven pieces of fruit. But this makes sense only if we thought ap- oles and oranges had equal value, which is generally not true. This would be even leaner if the economy had produced four watermelons and three grapes.) To compute the total value of different goods and services, the national in- come accounts use market prices because these prices reflect how much people are willing to pay for a good or service. Thus, if apples cost $0. 50 each and or nges cost $1.00 each, GDP would be GDP = (Price of Apples x Quantity of Apples +(Price of Oranges X Quantity of Oranges) (S0.50×4)+($1.00×3) GDP equals $5.00--the value of all the apples, $2.00, plus the value of all the Used Goods When the Topps Company makes a package of baseball cards and ells it for 50 cents. that 50 cents is added to the nation's gDP But what about when a collector sells a rare Mickey Mantle card to another collector for $500? That $500 is not part of GDP GDP measures the value of currently produced goods and services. The sale of the Mickey Mantle card reflects the transfer of ar sset, not an addition to the economy s income. Thus, the sale of used goods t included as part of GDP. The Treatment of Inventories Imagine that a bakery hires workers to produce more bread, pays their wages, and then fails to sell the additional bread. How does this transaction affect GDP? The answer depends on what happens to the unsold bread. Let's first suppos that the bread spoils. In this case, the firm has paid more in wages but has not re- eived any additional revenue, so the firms profit is reduced by the amount that wages are increased. Total expenditure in the economy hasnt changed because no one buys the bread. Total income hasn't changed either--although more distributed as wages and less as profit. Because the transaction affects neither ex- penditure nor income, it does not alter GDP. Now suppose, instead, that the bread is put into inventory to be sold later. In this case, the transaction is treated differently. The owners of the firm are assumed to have"purchased"the bread for the firms inventory, and the firms profit is not User JOENA: Job EFF01418: 6264_ch02: Pg 19: 24937#/eps at 1004 I l Tue,Feb12,20028:404M

User JOEWA:Job EFF01418:6264_ch02:Pg 19:24937#/eps at 100% *24937* Tue, Feb 12, 2002 8:40 AM domestic product (GDP) is the market value of all final goods and services produced within an economy in a given period of time. To see how this definition is applied, let’s dis￾cuss some of the rules that economists follow in constructing this statistic. Adding Apples and Oranges The U.S. economy produces many different goods and services—hamburgers, haircuts, cars, computers, and so on. GDP combines the value of these goods and services into a single measure.The diver￾sity of products in the economy complicates the calculation of GDP because different products have different values. Suppose,for example,that the economy produces four apples and three oranges. How do we compute GDP? We could simply add apples and oranges and conclude that GDP equals seven pieces of fruit. But this makes sense only if we thought ap￾ples and oranges had equal value, which is generally not true. (This would be even clearer if the economy had produced four watermelons and three grapes.) To compute the total value of different goods and services, the national in￾come accounts use market prices because these prices reflect how much people are willing to pay for a good or service.Thus, if apples cost $0.50 each and or￾anges cost $1.00 each, GDP would be GDP equals $5.00—the value of all the apples, $2.00, plus the value of all the oranges, $3.00. Used Goods When the Topps Company makes a package of baseball cards and sells it for 50 cents, that 50 cents is added to the nation’s GDP. But what about when a collector sells a rare Mickey Mantle card to another collector for $500? That $500 is not part of GDP. GDP measures the value of currently produced goods and services.The sale of the Mickey Mantle card reflects the transfer of an asset, not an addition to the economy’s income.Thus, the sale of used goods is not included as part of GDP. The Treatment of Inventories Imagine that a bakery hires workers to produce more bread, pays their wages, and then fails to sell the additional bread. How does this transaction affect GDP? The answer depends on what happens to the unsold bread. Let’s first suppose that the bread spoils. In this case, the firm has paid more in wages but has not re￾ceived any additional revenue, so the firm’s profit is reduced by the amount that wages are increased. Total expenditure in the economy hasn’t changed because no one buys the bread. Total income hasn’t changed either—although more is distributed as wages and less as profit. Because the transaction affects neither ex￾penditure nor income, it does not alter GDP. Now suppose, instead, that the bread is put into inventory to be sold later. In this case, the transaction is treated differently. The owners of the firm are assumed to have “purchased’’ the bread for the firm’s inventory, and the firm’s profit is not GDP = (Price of Apples × Quantity of Apples) + (Price of Oranges × Quantity of Oranges) = ($0.50 × 4) + ($1.00 × 3) = $5.00. CHAPTER 2 The Data of Macroeconomics | 19