How closely can we match/implement the classical assumptions in practice? Do some deviations from classical assumptions constitute negligible frictions or do they seriously challenge the predictive power of competitive equilibrium pricing? Are there "real" market institutions for which the competitive equilibrium is a good predictor of price and quantity outcomes? How do different market institutions affect efficiency and convergence to the competitive equilibrium? Do competitive markets disseminate and aggregate information sufficiently so that all traders with limited private information act as if they new all information available in the market