The Information Content of Daily Market Indicators

The theory of efficient capital markets indicates that the prices in an efficient market fully reflect all available information. In much of the literature on efficient markets the term fully reflect is made operational with the assumption that the conditions for market equilibrium can be expressed as expected returns. Fama suggests that most expected return theories can be expressed in the following manner:(1) where — adopting Fama's notation — E is the expected value operator; Pjt is the price of security j at time t; Pj,t+1 is its price at t+1; is the one-period percentage return (Pj,t+1|Pjt); φt is a general symbol to represent whatever set of information is assumed to be fully reflected in the price at time t; and the tildes indicate that Pj,t+1 and rj,t+1 are random variables at t.