Strategy-Proofness Versus Efficiency In Matching With Indifferences: Redesigning The New York City High School Match

The design of the New York City (NYC) High School match involved tradeoffs among efficiency, stability and strategy-proofness that raise new theoretical questions. The authors analyze a model with indifferences - ties - in school preferences. Simulations with field data and the theory favor breaking indifferences the same way at every school - single tie breaking - in a student-proposing deferred acceptance mechanism. Any inefficiency associated with a realized tie breaking cannot be removed without harming student incentives. Finally, they empirically document the extent of potential efficiency loss associated with strategy-proofness and stability, and direct attention to some open questions.