[WP-016] Ekkyo Matching: How to Integrate Fragmented Matching Markets for Welfare Improvement


Yuichiro Kamada, Fuhito Kojima


We consider a school-choice matching model that allows for inter-regional transfer of students (ekkyo admission), with the “balancedness” constraint: each student and school belongs to a region, and a matching is said to be balanced if, for each region, the out ow of students from that region to other regions is equal to the in ow of students from the latter to the former. Using a directed bipartite graph defined on students and schools, we characterize the set of Pareto efficient matchings among those that are individually rational, balanced and fair. We also provide a class of polynomial-time algorithms to compute such matchings. The outcome of an algorithm from this class weakly improves student welfare upon the one produced when each region independently uses a deferred acceptance algorithm.