Idiosyncratic Risk and the Cross-Section of Expected Stock Returns

• Main Author: FU, Fangjian
• Format: text
• Language: English
• Published: Institutional Knowledge at Singapore Management University 2009
• Subjects: Idiosyncratic risk; Cross-sectional returns; Time varying; Finance and Financial Management; Portfolio and Security Analysis
• Online Access: https://ink.library.smu.edu.sg/lkcsb_research/3030; https://ink.library.smu.edu.sg/context/lkcsb_research/article/4029/viewcontent/FuFJ2009IdiocyncraticRisk.pdf
• Institution: Singapore Management University

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.