Prospect Theory and Stock Returns During Bubbles

Abstract

I test the hypothesis that investors evaluate stocks based on the prospect theory value of the distribution of past returns. Because some investors tilt towards stocks with high prospect theory value, these stocks become overvalued and earn low subsequent returns. During bubbles this effect should be stronger, due to rising limits to arbitrage and increased participation of individual investors. I do not find strong support for this prediction in the cross section of returns in U.S. stock markets. In contrast to other variables know to explain returns however, prospect theory value does not lose its predictive power during bubbles. Investors with prospect theory preferences seem to choose stocks whose returns optimally combine low standard deviation with high skewness.

Keywords: Prospect Theory; bubbles; limits to arbitrage; individual investors.