We find that Robinhood ownership changes are unrelated with future returns, suggesting that zero-commission investors behave as noise traders. We exploit Robinhood platform outages to identify the causal effects of commission-free traders on financial markets. Exogenous negative shocks to...

Using a large panel of U.S. accounts trades and positions, we show that retail investors trade as contrarians after large earnings surprises, especially for loser stocks, and such contrarian trading contributes to post earnings announcement drift (PEAD) and momentum. Indeed, when we double-sort...