曼昆宏观总需求与总供给.pptVIP

* Of the three theories, this one seems the least plausible. Firms certainly have a strong incentive to not mistake a general price increase for a relative price increase. And information about the price level is costless and available with only a short lag (especially the CPI, which is published monthly and very widely reported the moment it comes out). My remarks here are not officially part of the textbook, so they are not supported in the study guide or test bank. Feel free to ignore them. * Economists debate which of these theories is correct. It’s possible that each of them contains some element of truth. For our purposes here, the similarities between these theories are more important than their differences: all three imply that output deviates from its long-run level (the “natural rate of output”) when the price level (P) deviates from the level people had expected (PE). * The preceding slide introduced an equation of aggregate supply that shows how output deviates from full-employment when the actual price level is different than expected. This slide illustrates these concepts using a graph. When P = PE, Y = YN When P PE, Y YN When P PE, Y YN * Notice that when the price level equals the expected price level, output is equal to its long-run value, the natural rate of output. Interpretation: In the short run, people may be fooled about the price level, or they may be locked into wages or prices that were set before they knew what the price level would actually be. Hence, in the short run, P may differ from PE. But in the long run, expectations catch up to reality, P = PE, and therefore Y = YN, as in the Classical model. Thus, our theory of economic fluctuations is basically the Classical model (which we studied for several chapters) augmented with some kind of market imperfection (such as sticky wages). The impact of the market imperfection occurs only in the short run, so the long-run behavior of our model