We provide novel evidence supporting the notion that arbitrageurs can contribute to return comovement via ETF arbitrage. Using a large sample of U.S. equity ETF holdings, we document the link between measures of ETF activity and return comovement at both the fund and the stock levels, after...

We design a new test for diseconomies of scale at the mutual fund level, and document that quarterly changes in fund performance are negatively related to lagged predicted fund flows. The effect is economically and statistically significant for both inflows and outflows. Results hold for factor...