Expectational Equilibria and Drèze Equilibria in Many-to-one Matching Models

We study coalition formation in many-to-one matching models from a competitive equilibrium perspective. We cover both models with and models without monetary transfers. A first notion to do so is the one of Drèze equilibrium, which we extend to the many-to-one set-up. A second concept is expectational equilibrium. It turns out that under very weak assumptions, we obtain an equivalence between these concepts, so both lead to exactly the same predictions. Since the equivalence might be between empty sets, we also present sufficient conditions for the existence of an equilibrium. The existence proof is based on an adjustment process.