We show that unconditionally efficient returns do not achieve the maximum unconditional Sharpe ratio, neither display zero unconditional Jensen’s alphas, when returns are predictable. Next, we define a new type of efficient returns that is characterized by those unconditional properties. We...

Contrary to the classic framework of passive strategies, if investors exploit return predictability through active strategies then there is a tension between the mean-variance frontiers that drive empirical work and the mean-variance preferences that are used in finance theory. We show that...