多恩布什Chap021.doc

21 Advanced Topics focus of the chapter ? This chapter presents an overview of four recent ideas and models that have revolutionized modern macroeconomics(rational expectations modeling, the random walk theory of GDP, real business cycle theory, and New Keynesian models of price stickiness. Not all of these ideas fit together(some, in fact, contradict each other. ? Much of the technical material developed in this chapter is optional, or even super-optional(you may or may not be required to work through it. Chapters 8 and 17 provide very readable policy implications of the ideas developed here. If you read nothing else, read those. section summaries 1. An Overview of the New Macroeconomics This section provides an informal introduction to four subjects: rational expectations modeling, the random walk theory of GDP, real business cycle theory, and New Keynesian models of price stickiness. We discuss each briefly, noting how each is related to the traditional aggregate supply-aggregate demand model. The rational expectations model outlined in this chapter (the Lucas model) tries to explain how output can deviate from potential output and unemployment from its natural rate without requiring that prices adjust sluggishly. We took a preliminary, non-technical look at this model in Chapter 6 (Section 6–3). You may recall some of the following: In Lucas’s model, people cannot directly observe the price level, and must therefore form expectations of it. When these expectations are wrong, people’s estimates of the real wage are also wrong, which causes them to supply “too much” or “too little” labor(an amount greater or less than they would choose to supply if they knew what their real wage really was. The labor market does clear in this model; the main way in which the aggregate supply assumptions differ from the classical case of the AS-AD model is that the labor supply, in this case, depends on the expected real wage rather than the actual real wage.