Financial markets provide a useful reminder of just how humble we economists should be about our understanding of the world. The three winners of the 2013 Nobel Memorial Prize in Economic Sciences neatly capture this tension.

Eugene Fama is the intellectual godfather of the view that financial markets are efficient, while no one has done more than Robert Shiller to highlight their inefficiencies. Lars Peter Hansen developed statistical techniques that both sides have used to help resolve their differences.

The central issue is whether the prices of stocks, bonds and other financial assets reflect the workings of a well-functioning market. That is, do financial prices reflect the wisdom of crowds, or do they mirror popular delusions? The answer determines whether you should try to beat the stock market, whether the Federal Reserve should respond to rising housing prices, and how the U.S. should regulate financial markets.