Sequential Pseudomarkets and the Weak Core in Random Assignments

We study random assignment economies with expectedutility agents, each of them eventually obtaining a single object. The assignment should respect object-invariant priorities such as seniority rights in student residence assignment, grandfather rights in landing slot assignment... We introduce the new Sequential Pseudomarket (SP) mechanism, where the set of agents is partitioned into ordered priority groups that are called in turns to participate in a pseudomarket for the remaining objects. We show that the set of all SP-equilibrium random assignments generated by every possible ordered partition coincides with the ex-ante weak core. Moreover, if we …x priority groups and individual budget limits, the resulting SP-equilibrium assignments are generically ex-ante Pareto-optimal.