The Common Factor in Idiosyncratic Volatility: Quantitative Asset Pricing Implications
NBER Working Paper No. 20076
We show that firms’ idiosyncratic volatility obeys a strong factor structure and that shocks to the common factor in idiosyncratic volatility (CIV) are priced. Stocks in the lowest CIV-beta quintile earn average returns 6.4% per year higher than those in the highest quintile. We provide evidence that the CIV factor is correlated with income risk faced by households. These three facts are consistent with a canonical incomplete markets heterogeneous-agent model. In the model, CIV is a priced state variable because an increase in idiosyncratic firm volatility raises the typical investor’s marginal utility when markets are incomplete. The calibrated model matches the high degree of comovement in idiosyncratic volatilities, the CIV-beta return spread, and several other asset price moments.
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Document Object Identifier (DOI): 10.3386/w20076