We explain the poor out-of-sample performance of mean-variance optimized portfolios, developing theoretical bias adjustments for estimation risk by asymptotically expanding future returns of portfolios formed with estimated weights. We provide closed-form non-Bayesian adjustments of classical...

A new technology is proposed for estimating the systematic (beta) risk of a firm's stock. Just as the implicit volatility of an asset is revealed by an ordinary call option, the "implicit beta" of a stock would be revealed by the price of an option to exchange shares of stock for shares of a...

This paper makes indirect inference about the time variation in expected stock returns by comparing unconditional sample variances to estimates of expected conditional variances. The evidence reveals more predictability as more information is used, and there is no evidence that predictability...

Practitioners needing estimates of a firm's equity cost of capital have long relied on the Capital Asset Pricing Model (CAPM). Recent evidence casts renewed doubt on the validity of the CAPM and beta. However, there is not much evidence to gauge the importance of the rejections of the CAPM in a...