That view underlies the government's entire case. The alleged monopoly enables Microsoft to force adverse terms on other companies and harm rivals by, for instance, bundling its Web browser with Windows and giving it away. This view is rife with fallacies. That leaves a not insignificant 10 to 15 percent for competitors. But this gives the government too much credit.
Market share depends on how the market is defined.
Alan Reynolds has shown that the government narrowly defines the market to further its case. When all this is taken into account, Reynolds calculates that Microsoft's Windows was on no more than 70 percent of the PCs delivered last year. Another problem for the judge's monopoly theory is the ever-present potential competition. Entrepreneurs and venture capitalists are always looking for high returns. Potential competition can soon become actual.