Short-Sale Constraints and the Idiosyncratic Volatility Puzzle: An Event Study Approach
56 Pages Posted: 24 Sep 2007 Last revised: 16 Jul 2014
Date Written: February 25, 2014
Using three natural experiments, we test the hypothesis that investor overconfidence produces overpricing of high idiosyncratic volatility stocks in the presence of binding short-sale constraints. We study three events: IPO lockup expirations, option introductions, and the 2008 short-sale ban on financial firms. Consistent with our prediction, we show that when short-sale constraints are relaxed, event stocks with high idiosyncratic volatility tend to experience greater price reductions, as well as larger increases in trading volume and short interest, than those with low idiosyncratic volatility. These results hold when we benchmark event stocks with non-event stocks with comparable idiosyncratic volatility. Overall, our findings suggest that biased investor beliefs and binding short-sale constraints contribute to idiosyncratic volatility overpricing.
Keywords: Idiosyncratic Volatility, Short-Sale Constraints, IPO Lockup, Option Introduction, Short-Sale Ban
JEL Classification: G12, G14, G18
Suggested Citation: Suggested Citation