We use novel data on individual activity in a sports betting market to study the effect of past performance sequences on individual behavior in a real market. The revelation of fundamental values in this market enables us to disentangle whether behavior is caused by sentiment or by superior...

High sentiment predicts low market returns and high arbitrage returns. This empirical evidence has important implications for portfolio optimization. Exploiting the eigenvalue-decomposition of the mean-variance portfolio, I show that its performance is the sum of two components: a market...