Pure competition and pure monopoly are the exceptions, not the rule, in the U.S. economy. In this chapter, the two market structures that fall between the extremes are discussed. Monopolistic competition contains a considerable amount of competition mixed with a small dose of monopoly power. Oligopoly, in contrast, implies a blend of greater monopoly power and less competition.
First, monopolistic competition is defined, listing important characteristics, typical examples, and efficiency outcomes. Next we turn to oligopoly, surveying the possible courses of price, output, and advertising behavior that oligopolistic industries might follow. Finally, oligopoly is assessed as to whether it is an efficient or inefficient market structure.