Government influences the course of business in many ways. Examples are tax and tariff policy, laws that aim to prevent fraud or misrepresentation, and price controls. But our interest is in government policies that concern market performance.

Such policies fall into three broad categories: public ownership, regulation of private enterprise and what in the United States is called antitrust policy, by which the government sets the rules according to which independent firms compete. As we will see, much of industrial economics has direst policy implications for antitrust policy.

Although antitrust laws now exist in many western nations, they received their earliest and fullest development in the United States during a period covering the end of the nineteenth century and the early decades of the twentieth century. The U.S. antitrust laws have been amended from time to time since then, sometimes in important ways. But they still reflect the character of the economy and society of the United States at that time. In this chapter, we introduce the antitrust laws of the United States and discuss the concern that led to their passage.