Final answer:
The wireless telecommunications industry's domination by Verizon, AT&T, Sprint, and T-Mobile exemplifies an oligopoly, with these carriers having significant market power and mirroring each other's business practices. Antitrust policies seek to prevent such market concentration to preserve competition, which is measured by metrics like the four-firm concentration ratio.
Step-by-step explanation:
The wireless telephone industry being dominated by four carriers: Verizon, AT&T, Sprint, and T-Mobile is an example of an industry structure known as an oligopoly. An oligopoly is a market form in which a market or industry is dominated by a small number of large sellers. The carriers mentioned have significant market power and, though they compete with one another, they also often follow one another’s lead in terms of pricing and services due to the high level of interdependence.
The antitrust policies aim to prevent mergers that would significantly reduce competition in the marketplace, as seen in the blocked merger between AT&T and BellSouth in 2006. The aim of these policies is to maintain competitive markets for the benefit of consumers and the economy. The four-firm concentration ratio is a measure used to assess the extent of competition in an industry by indicating the total market share, in percentage terms, held by the four largest firms in the market. A high concentration ratio indicates that the industry is dominated by a few firms and is less competitive.