In empirical studies of the CAPM, it is commonly assumed that, (a) the return to the value-weighted portfolio of all stocks is a reasonable proxy for the return on the market portfolio of all assets in the economy, and (b) betas of assets remain constant over time. Under these assumptions, Fama...

In the context of futures markets, we study whether brokers allocate more favorable trades to their own accounts, and less favorable trades to their customers. We find that, within a thirty minute trading bracket, brokers on average buy at a lower price and sell at a higher price for their own...