MULTIPRODUCT CLUBS - MEMBERSHIP AND SUSTAINABILITY

Club theory is extended to the case of multiproduct clubs. Multiproduct club structure varies depending on whether members are restricted to consume all of the club's products, and whether the club is sustainable against other clubs providing the entire package of products or a subset. Membership of the multiproduct club is contrasted to that of alternative clubs serving a subset of products. Necessary conditions for sustainability are related to cost subadditivity and membership restrictions. The integer problem and the instability that it entails for club memberships are more troublesome for multiproduct clubs, because the population must be partitioned by both products and clubs.