"We use a two-year panel of individual accounts in an S&P 500 index mutual fund to examine the trading and investment behavior of more than 91 thousand investors who have chosen a low-cost, passively managed vehicle for savings.... We find that more frequent traders are typically contrarians, while infrequent traders are more typically momentum investors.... We find that the behavior of momentum investors is typically more correlated to changes in the S&P 500 and we trace its dynamics over time."  MORE >>