We analyze trading records for 66,465 households at a large discount broker and 665,533 investors at a large retail broker to document that the trading of individuals is highly correlated and persistent. This systematic trading of individual investors is not primarily driven by passive reactions to institutional herding, by systematic changes in risk-aversion, or by taxes. Psychological biases likely contribute to the correlated trading of individuals. These biases lead investors to systematically buy stocks with strong recent performance, to refrain from selling stocks held for a loss, and to be net buyers of stocks with unusually high trading volume.

I review the recent literature on cross-sectional predictors of stock returns. Predictive variables used emanate from informal arguments, alternative tests of risk-return models, behavioural biases, and frictions. More than fifty variables have been used to predict returns. The overall picture, however, remains murky, because more needs to be done to consider the correlational structure amongst the variables, use a comprehensive set of controls, and discern whether the results survive simple variations in methodology.