In: Economics
The firm must have dominant position in the market and is able to create entry barriers for other firms to avoid competition. There must be abusive use of dominant position by the monopolist. A dominant firm must act to harm the competitive process as opposed to competitors. When the anticompetitive efforts of the monopolist outweigh the procompetitive efforts, the firm is liable for prosecution under Sherman Act.
Microsoft was found to have used contracts that severely disadvantaged the competing browsers. Original Equipment Manufacturers were prohibited from altering windows desktop and initial boot sequence. It was decided and concluded that such activity rather than improving the position of the Microsoft browser, led to its fall. Microsoft was declared monopoly but judge held that the share was quite large and stable and it is protected by a high entry barrier. One reason was that Microsoft lacked a commercially viable alternative to Windows.