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宏观经济学教师资源扩展资料课堂讲稿 第十版 曼昆 人大社

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The Science of Macroeconomics
Notes to the Instructor
Chapter Summary
Chapter 1 presents a brief introduction to macroeconomics. The chapter explains the type of questions macroeconomists address, introduces the concept of an economic model, and discusses the roles of price flexibility and price stickiness in macroeconomic models.
The amount of introduction required naturally depends upon the students’ previous exposure to macroeconomics in principles or in other courses. I try to stress the relevance of macroeconomics; a good way to do this is to bring in copies of that day’s newspapers and show how they contain stories related to the course. I also stress the importance of basic macroeconomic literacy and emphasize that macroeconomics teaches a way of thinking about and understanding the economy rather than a set of facts. I highlight how models help us focus on essentials and avoid unnecessary distractions that can lead us astray. One way to do this is to show how common sense can sometimes give incorrect answers; an example from the textbook is that protectionist policies don’t improve the trade balance.
The supply and demand model presented in Chapter 1 provides a vehicle to explain the role of microeconomics in macroeconomics and to show how macroeconomics uses many tools and ideas from microeconomics. The lecture notes emphasize this and also explain how macroeconomics differs from microeconomics in its level of aggregation and in that it has more of a general-equilibrium focus. The textbook works, as do economists, by using different models to answer different questions, but I reassure students that we also emphasize how different models fit together.
The companion website for students and instructors has been updated for use with the 10th edition of Macroeconomics ( The site offers a superb set of software-based features and a PowerPoint® tutorial for students. In addition, the PowerPoint slides for instructors have been updated and include animated graphics and other innovative pedagogical features.
Students will find the website both helpful and fun to use. The website includes Self-Tests and Flashcards that provide immediate feedback to students, a Data Plotter that students can use to graph and compare macroeconomic data, a feature titled A Game for Macroeconomists that allows students to make policy choices as president of the United States, and a Macro Models component that provides students with the hands-on opportunity to manipulate the models of the textbook. These software features can be used simply as a source of additional exercises for students to do on their own, or they can be incorporated directly into classroom discussions. For example, to integrate the software into a class, students might be given an assignment to develop a policy memo for the president that requires the use of both the Macro Models feature and the Data Plotter. The instructor might then run a mock cabinet meeting and have students present their findings and policy recommendations. The software also can be used to design advanced essay questions for students. Some possibilities and suggestions for using the software are provided in the Notes to Instructors section of subsequent chapters.
The student resource titled Student PowerPoint Tutorials provides students with an animated set of slides that will help reinforce the material from the text and lectures. This tutorial uses superb graphics and a dose of humor to enliven macroeconomics. A good way of incorporating this feature is to suggest that students view the slides after reading each chapter to help deepen their understanding.
For enhancing your classroom lectures, I strongly recommend the use of the PowerPoint slides for instructors that are available on the website. This resource includes explanations of the text’s models and case studies, along with notes to instructors. The presentations are organized by chapter, and you can easily augment them by inserting your own slides.
Use of the Website
The website provides a rich source of data for supplementing lectures and designing class projects. A good use of this resource for Chapter 1 is to create graphs of real GDP growth, CPI inflation, and the unemployment rate over the past few years to provide an up-to-date picture of the economy’s main economic indicators. Locate the data on the website’s data page and choose the appropriate settings to create a graph.
Chapter Supplements
This chapter includes the following supplements:
1-1        The Recent Behavior of the U.S. Economy: A Guide to the Case Studies
1-2        Presidential Elections and the Economy
1-3        When Is the Economy in a Recession?
1-4        Economic Rhetoric
1-5        Additional Readings
Lecture Notes
1-1        What Macroeconomists Study
Economics is the study of how people, businesses, and governments behave and interact in the production and allocation of goods and services. Traditionally, economics is divided into microeconomics, which studies the behavior of individuals and organizations (consumers, firms, and the like) at a disaggregated level, and macroeconomics, which studies the overall or aggregate behavior of the economy. Since this book studies macroeconomics, we seek to explain phenomena such as inflation, unemployment, and economic growth, and we are not concerned with, say, the demand for or supply of peanuts.
In macroeconomics, we do two things. First, we seek to understand the economic functioning of the world we live in; and second, we look at whether we can do anything to improve the performance of the economy. That is, we are concerned with both explanation and policy prescriptions.
Explanation involves an attempt to understand the behavior of economic variables, both at a moment in time and as time passes. Modern macroeconomics recognizes that it is important to focus on more than just short periods of time, and so it has an explicitly dynamic focus. We thus try to explain the behavior of economic variables over time. This means that we wish to explain the behavior of the economy both in the long run and in the short run.

        Supplement 1-1, “The Recent Behavior of the U.S. Economy”
        Figure 1-1
        Figure 1-2
        Figure 1-3
        Supplement 1-2, “Presidential Elections and the Economy”
        Supplement 1-3, “When Is the Economy in a Recession?”
Case Study: The Historical Performance of the U.S. Economy
Perhaps the three most important indicators of the macroeconomic performance of an economy are real gross domestic product (GDP), the inflation rate, and the unemployment rate. Real GDP is a measure of the quantity of goods and services produced in the economy in a given year. The historical record shows that real GDP has risen substantially over time, although this growth is irregular, and there are periods when output actually falls. The inflation rate is a measure of how prices are changing, on average. The inflation rate has usually been positive but low in the United States, indicating that prices have tended to go up on average, but not at a particularly rapid pace. There have been periods in U.S. history when prices have tended to fall. The unemployment rate measures the percentage of those who are seeking work but do not have jobs. There is always some unemployment in the U.S. economy, although the level fluctuates substantially. The unemployment rate has generally been less than 10 percent but rose to 25 percent during the Great Depression.
1-2        How Economists Think
Theory as Model Building
A key element of economic analysis—both microeconomic and macroeconomic—is the study of markets and prices. In an economy, goods are traded and exchanged. We think about this as taking place in markets. The economist’s idea of a market is an abstract representation of a real market, where, for example, farmers might bring their produce for sale. Economists analyze markets by thinking about suppliers and demanders of goods. As an example, consider the market for pizza. Thinking first about the supply of pizza, an economist might posit that the number of pizzas that pizzerias will put up for sale depends on the price of pizza: the higher the price, the more pizza supplied. An economist might also think that the supply of pizza depends on the cost of the materials, such as tomatoes and cheese. The higher the cost of cheese, the fewer pizzas will be supplied at any given price of pizza. Turning to the demand for pizza, an economist might think that the number of pizzas that consumers will want to buy will depend on the price of pizza and on consumers’ aggregate income.
If we suppose that the price of pizza adjusts so that demand equals supply, we add an equilibrium condition to our representation of the pizza market, whereby the supply of pizza (Qs) equals the demand for pizza (Qd):
Qs = Qd.
In terms of a graph, this is equivalent to looking for the point where the supply and demand curves meet. We return to this example shortly.
The economy is a complicated system. Every day, millions of people make economic decisions. They buy their morning coffee, they buy lunch, they withdraw money from their checking accounts, they go to movies, they buy clothes, and they sell old textbooks. All of these are economic decisions with implications for the economy. In macroeconomics, we are trying to understand the way that the whole economy works. But, obviously, we cannot consider every individual transaction in every market in the economy. Instead, we have to simplify; we have to abstract from reality; we have to focus on what is important and discard what is unimportant.
To try to understand the economy and focus on what is important, we do a couple of things. First, we aggregate. Instead of worrying about individual goods—pizza, bread, automobiles, peanuts, and the like—we think about some aggregate of them all. We call this good real GDP and denote it by the symbol Y. GDP stands for gross domestic product. It is a measure of the total production in the economy; indeed, explaining the behavior of the economy is largely a matter of explaining the behavior of real GDP over time. We consider the definition of GDP more carefully later.
The second thing we do is to build models. Models are abstractions from reality that serve as frameworks of analysis. Just as aerospace engineers build model planes to put in a wind tunnel and judge that these models need not be equipped with “fasten seat belt” signs but should be equipped with wings, so economists construct representations of the economy that include important variables and exclude unimportant variables. Many different sciences, such as meteorology, physics, and biology, use models. In economics, as in many other sciences, the models with which we work are usually mathematical. We develop mathematical explanations of the economy and use algebra and graphs to help understand how the economy works. The aim of macroeconomics and this textbook is not so much to provide facts about macroeconomics as to give a framework of analysis for coherent thinking about macroeconomic issues.
The previous analysis of the pizza market is an example of a model. This model represents the determination of the equilibrium price and quantity traded in a simple setting. In constructing that model, we judged that the price of pizza, the price of cheese, and aggregate income are all important in understanding the demand for and supply of pizza; we implicitly decided that all other variables were less important and could be left out. Knowing what to include and what not to include in a model is the art of the economist; it requires judgment and skill.
We can use the model of the pizza market to answer certain questions. For example, we might wonder what effect an increase in consumers’ incomes might have on the price of pizza. An increase in income would imply that at any given P, consumers would demand more pizza. The demand curve would shift to the right. Thus, we see that price and quantity both rise. Similarly, an increase in the price of materials would cause the supply curve to shift in, raising the equilibrium price of pizza and lowering the quantity traded.
This experiment is typical of the way economists use a model. They change one variable, taken as given, and look at the effect on other variables that the model explains. Variables taken as given from outside the model are known as exogenous variables; variables explained within the model are known as endogenous variables. A typical experiment with an economic model thus involves changing an exogenous variable and looking at the effect on endogenous variables. This is known as a comparative static experiment.
FYI: Using Functions to Express Relationships Among Variables
Economists use mathematics—particularly graphs and algebra—to help understand the economy. For example, we have thus far said two things:
1.        The supply of pizza depends on the price of pizza and the price of materials.
2.        The demand for pizza depends on the price of pizza and aggregate income.
A mathematician uses symbols to express concepts such as these more compactly:
1.        Qs = S(P, Pm);
2.        Qd = D(P, Y).
Here S( ) and D( ) are functions: they indicate relationships among variables. Qs, Qd, P, Pm, and Y are variables, denoting the quantity of pizza supplied, the quantity of pizza demanded, the price of pizza, the price of materials, and aggregate income, respectively. An example of a supply function is
Qs = 15P – 2Pm.
Another example is
Qs = 13(P/Pm).
Very often in economics, we do not know very much about the exact nature of the relationships among variables, and so we prefer the general functional notation used earlier.

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