This paper decomposes the risk premia of individual stocks into contributions from systematic and idiosyncratic risks. I introduce an affine jump-diffusion model, which accounts for both the factor structure of asset returns and that of the variance of idiosyncratic returns. The estimation is...

"This paper finds strong evidence of time-variations in the joint distribution of returns on a stock market portfolio and portfolios tracking size--and value effects. Mean returns, volatilities and correlations between these equity portfolios are found to be driven by underlying regimes that...