Night trading: Lower risk but higher returns?

This paper demonstrates that overnight returns are subject to highly persistent biases and examines the profitability of overnight-only investments in that context. Overnight returns tend to exceed their intraday counterparts, and the paper first reconciles these patterns by introducing a model that factors in systematic biases. This model identifies one-fifth of stocks as having positive and statistically significant overnight biases. Investing overnight in these stocks in the next year yields twice the market's return for a third of the market beta. Results also have implications for daytime investors as these stocks underperform intraday. Implementation costs and issues are discussed.