Priorities vs. Precedence: Theory and Evidence from Boston

Discussion Paper

Umut Dur, Scott Duke Kominers, Parag A. Pathak, Tayfun Sonmez

January 2013

Boston’s school choice plan has a 50/50 split of school seats into a walk half and open half. This feature emerged as a compromise when the plan was formulated in 1999. When a choice plan has a slot-specific priorities like this, the precedence order, i.e. the order in which seats are depleted by applicants with specific claims, is a lever to achieve distributional goals that has effects comparable to priorities under the deferred acceptance algorithm. While Boston gives priority to neighborhood applicants in half of the seats at each school, the intended effect of this policy is almost fully lost because of the precedence order of the seats; its outcome is nearly equivalent to that of a mechanism without any neighborhood priority. This fact shows how the precedence order can undermine the intended role of priorities.