Firms raise cost-reducing alliances before competing with each other, but cannot fully internalize the shared knowledge. When spillovers are local and transit through the network of alliances, stable architectures with a moderate level of asymmetry are identified

We consider a Cournot oligopoly setting in which consumers have an intrinsic preference for variety, while unit production costs of firms increase with the number of goods they produce. This environment exhibits a general under-provision of variety with respect to social welfare.