Before revision:  Such stochastic market efficiency places strong constraints on the possible stochastic properties of the market.Historical data confirm the hypothesis .
After revision:  Such stochastic market efficiency places strong constraints on the possible stochastic properties of traded assets, which we call "leverage efficiency." Market conditions that deviate from leverage efficiency are unstable and may create leverage-driven bubbles. This result resolves the equity premium puzzle, informs interest rate setting, and constitutes a theory of noise in financial markets .