Contracting with Heterogeneous Externalities

We model situations in which a principal offers contracts to a group of agents to participate in a project. Agents' benefits from participation depend on the identity of other participating agents. We assume heterogeneous externalities and characterize the optimal contracting scheme. We show that the optimal contracts' payoff relies on a ranking, which arise from a tournament among the agents. The optimal ranking cannot be achieved by a simple measure of popularity. Using the structure of the optimal contracts, we derive results on the principal's revenue extraction and the role of the level of externalities' asymmetry.