Whether idiosyncratic volatility has increased over time and whether it is a good predictor of future returns is a matter of active debate. We show formally through central limit arguments that there is a direct relationship between the dynamics of the cross-sectional variance of realized...

While it is often argued that allocation decisions can be best expressed in terms of exposure to rewarded risk factors, as opposed to somewhat arbitrary asset class decompositions, the practical implications of this paradigm shift for the optimal design of the policy portfolio still remain...