This book examines methods for controlling or guiding a sector of the economy that do not require all the apparatus of economic planning or rely on the vain hope of sufficiently "perfect" competition, but instead rely entirely on the self-interest of economic agents and voluntary contract. The methods involved require trial-and-error steps in real time, with the target adjusted as the results of each step become known. The author shows that the methods are equally applicable to industries that are wholly privately owned, wholly nationalized, mixed or labor-managed.