Final answer:
Market definition is essential in antitrust law for assessing a company's market share and determining whether it holds a monopoly that can control prices or exclude competition. Legal cases, like the one against DuPont, highlight the importance of how markets are defined. As competition becomes more global, market definitions may broaden, but antitrust authorities must remain vigilant.
Step-by-step explanation:
The market definition plays a crucial role in determining illegal monopolization because it sets the boundaries within which market power is assessed. For instance, in the DuPont cellophane case, the company dominated the cellophane market but argued that its market was actually the broader 'flexible packaging materials' market, which includes a variety of products. The U.S. Supreme Court agreed with this broader definition, leading to the dismissal of the monopoly charges.
Similarly, considerations about whether Microsoft held a monopoly in computer operating systems had to account for its market share in the total market for all computer software and services. The definition of markets is essential for antitrust authorities to determine whether a firm has the power to control prices or exclude competition.
With increasing globalization, the expectation is that market definitions may become broader due to greater competition from distant places. Yet, this doesn't lessen the responsibility of antitrust authorities to monitor and act against potential monopolistic practices that may extend across national borders.