The relation between time-series and cross-sectional effects of idiosyncratic variance on stock returns in G7 countries

"This paper suggests that CAPM-based idiosyncratic variance (IV) correlates negatively with future stock returns because it is a proxy for loadings on discount-rate shocks in Campbell's (1993) ICAPM. The ICAPM also implies that there are important links between the time-series and cross-sectional IV effects. For example, the coefficients on conditional stock market variance and value-weighted average IV obtained from the time-series regressions reflect loadings on stock market returns and discount-rate shocks, respectively; therefore, they should help explain the cross section of stock returns. Moreover, we expect a close relation between the IV and book-to-market effects because recent studies show that the latter also reflects intertemporal pricing. These conjectures are strongly supported by the G7 countries data"--Federal Reserve Bank of St. Louis web site.