The Mortensen Rule and E¢ cient Coordination Unemployment". Unpublished paper

We apply the e ¢ ciency axioms of Mortensen (1982) to a set of match-ing games involving coordination frictions between buyers. These games include markets with \u85nite numbers of buyers and sellers and markets with in nite numbers of heterogenous buyers and homogenous sellers. We show that the Mortensen rule, but not the Hosios rule, gives constrained e ¢-cient allocations. We also show that the Mortensen rule is implemented by a simple auction.