Rational expectations equilibrium with conditioning on past prices: A mean-variance example

The paper uses an intertemporal mean-variance model of the market for a dividend-paying risky asset to analyse rational expectations equilibria when all agents condition their expectations on past rather than current prices. The main result shows that if the time span between successive market periods is short, the market will approximate full informational efficiency arbitrarily closely, yet the returns to being informed are bounded away from zero. This contrasts with the Grossman-Stiglitz proposition that markets cannot come close to informational efficiency if the acquisition of information is costly.