U.S. v. Microsoft: Where Did the Time Go?

Antitrust law enforcement is sometimes criticized for taking too long to obtain results. On the one hand, slowness has potentially harmful consequences for market competition, consumers and business. On the other hand, fast outcomes are perhaps more likely to contain errors in fact and assessment and less likely to form good precedent. To provide a detailed examination of length of process and potential market consequences, the U.S. v Microsoft antitrust case is examined. The case took more than six years between the government receiving a complaint and the end of the last court proceeding. During the investigations and court proceedings, Microsoft’s market share of browser usage rose from less than 20% to above 90%. After the conclusion of the case, its market share declined relatively consistently for many years. A structural breakpoint is found near the end of proceedings, consistent with the long-run efficacy of competition law.