On Monday the Nobel Committee announced the winners of the 2011 Nobel Prize in economics: Thomas J. Sargent of New York University and Stanford University's Hoover Institution, and Christopher A. Sims of Princeton University. The award was given for "their empirical research on cause and effect in the macroeconomy."
The Swedish economists announcing the award emphasized, correctly, the importance of Messrs. Sargent's and Sims's thinking about the role people's expectations play in economic decision making and the larger economy. But what they failed to mention is that their work has also offered empirical evidence that the school of thought known as Keynesian economics—which believes that government can turn a flagging economy around with the right combination of fiscal "stimulus" (generally government spending) and monetary policy—is fallible.
Mr. Sargent was an early and important contributor to the "rational expectations" revolution in macroeconomics, an area for which his sometime collaborator, Robert E. Lucas Jr., won the Nobel Prize in 1995. One of Mr. Sargent's key early contributions, along with University of Minnesota economist Neil Wallace, was the idea that people's expectations about government fiscal and monetary policy make it difficult for government officials to affect the economy in the ways they intend to.