Chapter 18 A survey of behavioral finance Behavioral finance argues that some financial phenomena can plausibly be understood using models in which some agents are not fully rational. The field has two building blocks: limits to arbitrage which argues that it can be difficult for rational traders to undo the dislocations caused by less rational traders; and psychology which catalogues the kinds of deviations from full rationality we might expect to see. We discuss these two topics and then present a number of behavioral finance applications: to the aggregate stock market to the cross section of average returns to individual trading behavior and to corporate finance. We close by assessing progress in the field and speculating about its future course.