(10)After iterating this process until the end of the sample we obtain a time series of ex post excess returns for each optimal portfolio. Denoting by the sample mean and by the sample variance of the portfolio return, we define two statistics to evaluate the performance of the trading strategies: the Sharpe ratio, which measures the risk-adjusted performance of the strategy, and the certainty equivalent return, which is the risk-free return that a mean-variance investor (with risk aversion λ) would consider equivalent to investing in the strategy. To test whether the SR of the strategy based on predictor X is equal to the SR of the strategy based on the historical mean of market return, denoted by SR0, we follow the approach of Jobson and Korkie (1981) and DeMiguel et al. (2009). We proceed in a similar way to test whether the CE of the strategy based on X is equal to the CE of the strategy based on the historical mean of market excess return, denoted by CE0.14 Finally, we compute the annual transaction fee generated by each strategy as where f is the fee per dollar and denotes the market weight just before rebalancing at .