Idiosyncratic volatility, stock market volatility, and expected stock returns

We find that the value-weighted idiosyncratic stock volatility and aggregate stock market volatility jointly exhibit strong predictive power for excess stock market returns. The stock market risk-return relation is found to be positive, as stipulated by the CAPM; however, idiosyncratic volatility is negatively related to future stock market returns. Also, idiosyncratic volatility appears to be a pervasive macrovariable, and its forecasting abilities are very similar to those of the consumption-wealth ratio proposed by Lettau and Ludvigson (2001).