I. Introduction, 41. — II. The equilibrium of the competitive firm, 42; the cost of uncertainty, 42; the economics of prediction, 46; prediction and profit, 48; prediction and supply, 51. — III. The equilibrium of the competitive industry, 54; prediction and profit in a closed industry, 55; prediction and economic equilibrium in an open industry, 58; prediction and price variation, 58; decentralization of prediction, 60. — IV. Conclusions, 61.