d States and Canada. Commentators generally agree that implicitly assuming that these cus- tomers were locked into Aspen caused the Supreme Court to define the geographic market too narrowly (Campbell 1985; Easterbrook 1986; Wiley 1986b; Lipsky and Sidak 1999; Areeda and Hovenkamp 2006b; Hovenkamp 2005). Furthermore, there is some evidence that Highlands was free riding on Ski Co.'s facilities and marketing efforts. For example, Highlands's inability to attract more than 18.5 percent of the overall business suggests that its ski area was below Networks in Telecommunications average in attractiveness. From this perspective, Highlands was simply diverting revenue from skiers attracted by the higher-quality mountains provided by Ski Co (Easterbrook 1986). Furthermore, Ski Co. purchased national advertising to bring vacationers to Aspen; Highlands did not. If Ski Co. were to advertise optimally, it should increase its advertising until the marginal return no longer exceeded the marginal cost of increasing advertising any further. To the extent that Highlands siphoned off some of the business generated by this advertising, Ski Co.'s returns to advertising would look artificially low and would cause Ski Co. to stop further advertising even when it would be efficient to continue to do SO. Highlands's free riding would thus ultimately impede Ski Co.'s ability to compete with other ski areas (Wiley 1986b). Another possible problem is that the pro rata division did not reflect the marginal benefits provided by each ski area. Although Highlands accounted for between 13.2 percent and 18.5 percent of the usage while the four-area pass was in use, its share eventually dropped to 11 percent after discontinuation of the pass (472 U.S. at 595). This suggests that its marginal contribution might be somewhat smaller than its pro rata usage might suggest. In other words, the value that skiers place on a four-area pass might be only 11 percent more than the value they would place on a three-area pass. Thus, the proportion in which sk