Efficiency and the provision of open platforms

Private firms may not have efficient incentives to allow third-party producers to access their platform or develop extensions for their products. Based on a two-sided market model, I discuss two reasons for why. First, a private firm may not be able to internalize all benefits from cross-group externalities arising with third-party extensions. Second, firms may have strategic incentives to shut out third-parties because it relaxes competition. -- Platforms ; Two-sided markets ; open versus closed