Idiosyncratic Risk and the Cross-Section of Expected Stock Returns

Publication Type

Conference Paper

Publication Date

8-2005

Abstract

Theories such as Merton (1987, Journal of Finance) predict a positive relation between idiosyncratic risk and expected return when investors do not diversify their portfolio. Ang, Hodrick, Xing, and Zhang (2006, Journal of Finance 61, 259-299) however find that monthly stock returns are negatively related to the one-month lagged idiosyncratic volatilities. I show that idiosyncratic volatilities are time-varying and thus their findings should not be used to imply the relation between idiosyncratic risk and expected return. Using the exponential GARCH models to estimate expected idiosyncratic volatilities, I find a significantly positive relation between the estimated conditional idiosyncratic volatilities and expected returns. Further evidence suggests that Ang et al.'s findings are largely explained by the return reversal of a subset of small stocks with high idiosyncratic volatilities.

Keywords

Idiosyncratic risk, Cross-sectional returns, Time varying

Discipline

Business

Publication

European Finance Association

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