With a growing popularity of index funds, we adopt a differences-in-opinion, general equilibrium framework to examine theoretically whether investors are better off with an index portfolio than active investing. In contrary to the conventional view, we find that, even for an active investor with...

We analyze optimal asset allocation in continuous time for a collective of tied-together investors. We rely on a specific collective utility function which dates back to Karatzas (1990), by which the fund manager maximizes the weighted average of expected individual utilities for the investors...

We present a general equilibrium model in which heterogeneous investors choose among bonds, stocks, and an Index Fund holding the market portfolio. We show that, under standard assumptions, an equilibrium exists. We then derive predictions for equilibrium asset prices, investor behavior, and...