In Aspen Skiing Co. v. Aspen Highlands Skiing Corp., 472 U.S. 585, 105 S.Ct. 2847, 86 L.Ed.2d 467 (1985), the defendant owned three of the four mountains in the Aspen, Colorado ski area, and the plaintiff owned the fourth mountain. They had jointly offered for many years a multiple-day, multiple-area ticket that gave skiers admission to all of the mountains (the "joint ticket"). Aspen Skiing, 472 U.S. at 589-90, 105 S.Ct. 2847. The joint ticket was often cheaper than purchasing multiple single-day tickets. Id. at 589, 105 S.Ct. 2847. Revenues from the joint ticket were divided between the parties according to the relative percentage that buyers with the joint ticket used each mountain. Id. The defendant decided to discontinue the joint ticket by giving the plaintiff "an offer that it could not accept": the defendant would continue participating in the joint ticket only if the plaintiff agreed to receive a fixed percentage of joint ticket revenues that was considerably lower than the historical average based on actual usage of the fourth mountain. Id. at 592, 105 S.Ct. 2847. After the plaintiff rejected the offer, the defendant sold a joint ticket featuring only its three mountains. Id. at 593, 105 S.Ct. 2847. The plaintiff attempted to market its own multiple-day, multiple-area package by offering ski passes to the fourth mountain along with vouchers, each equal to the retail price of a single-day ticket to one of the defendant's mountains. Id. at 593-94, 105 S.Ct. 2847. The defendant refused to accept these vouchers and to sell any lift tickets to the plaintiff at retail price. The Supreme Court upheld a jury verdict in favor of the plaintiff on its claim that the defendant had monopolized the market for downhill skiing services in Aspen. Id. at 605, 105 S.Ct. 2847.