The antitrust laws prohibit conduct by a single firm that unreasonably restrains competition by creating or maintaining monopoly power. Most Section 2 claims involve the conduct of a firm with a leading market position, although Section 2 of the Sherman Act
The antitrust laws prohibit conduct by a single firm that unreasonably restrains competition by creating or maintaining monopoly power. Most Section 2 claims involve the conduct of a firm with a leading market position, although Section 2 of the Sherman Act also bans attempts to monopolize and conspiracies to monopolize. As a first step, courts ask if the firm has "monopoly power" in any market. This requires in-depth study of the products sold by the leading firm, and any alternative products consumers may turn to if the firm attempted to raise prices. Then courts ask if that leading position was gained or maintained through improper conduct—that is, something other than merely having a better product, superior management or historic accident. Here courts evaluate the anticompetitive effects of the conduct and its procompetitive justifications.
Courts do not require a literal monopoly before applying rules for single firm conduct; that term is used as shorthand for a firm with significant and durable market power — that is, the long term ability to raise price or exclude competitors. That is how that term is used here: a "monopolist" is a firm with significant and durable market power. Courts look at the firm's market share, but typically do not find monopoly power if the firm (or a group of firms acting in concert) has less than 50 percent of the sales of a particular product or service within a certain geographic area. Some courts have required much higher percentages. In addition, that leading position must be sustainable over time: if competitive forces or the entry of new firms could discipline the conduct of the leading firm, courts are unlikely to find that the firm has lasting market power.
Judging the conduct of an alleged monopolist requires an in-depth analysis of the market and the means used to achieve or maintain the monopoly. Obtaining a monopoly by superior products, innovation, or business acumen is legal; however, the same result