nopolize . . . any part of the trade or commerce among the several States, or with foreign nations . . . ." It defines anti-competitive as possession of monopoly power in the relevant market and the willful acquisition or maintenance of power. As in the United States v. Grinnell Corp. (1966) , the Court first had to determine the boundaries of the commercial activity that is termed the "relevant market." The evidence presented at trial proved that there are currently no products - and that there are not likely to be any in the near future - that a significant percentage of computer users worldwide could substitute for Intel-compatible PC operating systems without incurring substantial costs. The Court inferred that if a single firm or cartel controlled the licensing of all Intel-compatible PC operating systems worldwide, it could set the price of a license substantially above that normally charged in a competitive market. It could also leave the price there for a significant period of time without losing so many customers as to make the action unprofitable. This inference, in turn, led the Court to find that the licensing of all Intel-compatible PC operating systems worldwide did indeed constitute the relevant market claimed by the plaintiffs.The plaintiffs, according to Justice Jackson, also proved that Microsoft's dominant market share is protected by the applications barrier to entry. This barrier ensures that no Intel-compatible PC operating system other than Windows met consumer needs, and that the barrier would operate to the same effect even if Microsoft held its prices substantially above the competitive level for an extended period of time. Together, proof of dominant market share and the existence of a substantial barrier to effective entry created the belief that Microsoft enjoys monopoly power for the Court. In cases enforcing Section Two of the Sherman Act, once it is proved that the defendant possesses monopoly ...
