2011诺贝尔经济学奖获奖演说英文.doc

Award Ceremony Speech Presentation Speech by Professor Per Krusell, Member of the Royal Swedish Academy of Sciences, Chairman of the Economics Sciences Prize Committee, 10 December 2011 Your Majesties, Your Royal Highnesses, Laureates, Ladies and Gentlemen,Our national economies are continuously exposed to changes in the world around us. Fluctuations in the economic activity of other countries influence foreign demand for our products; variations in the prices of raw materials influence our production costs; technical innovations change the mix of goods and services demanded. Evaluating alternative responses to these sorts of inevitable economic disturbances is a central task for policymakers. How much, for example, would a particular increase in interest rates or decrease in income taxes affect the nation’s inflation and employment? And how long before those effects would be realised? Macroeconomic questions like these are hard to answer, because they are fundamentally social science questions. Unlike natural scientists, economists cannot look for answers by conducting controlled experiments, at least not on whole economies. We must work instead with the data provided by history. In addition, economies do not behave like mechanical, natural science systems. Nature obeys its laws independently of what governments decide, but economies do not, because economies consist of thinking people. Thinking people are also influenced by expectations about the future. For this reason, economies are also influenced by expectations of future policy decisions not yet made. This makes the co-variations observed in historical data hard to interpret. Does a particular historical change in an interest rate explain the subsequent change in the inflation rate? Or is the causality the reverse: did the expected path of inflation generate the interest rate change? In general, how can we distinguish between cause and effect in a macroeconomy? Thomas Sargent and Christopher Sims have prov