Aggregate idiosyncratic volatility in G7 countries

The paper analyzes average idiosyncratic volatility in G7 countries. We find that idiosyncratic volatility is highly correlated across countries and there is a significant Granger causality from the U.S. to the other countries and vice versa. Consistent with U.S. data, when combined with stock market volatility, idiosyncratic volatility has significant predictive power for stock market returns and the value premium in many other G7 countries. Moreover, in U.S. data, idiosyncratic volatility has explanatory power for stock returns very similar to that of value premium volatility in both time-series and cross-sectional regressions. Our results suggest that idiosyncratic volatility proxies for systematic risk omitted from CAPM.