Minimally Unstable Pareto Improvements over Deferred Acceptance

37 Pages Posted: 12 Nov 2020 Last revised: 8 Jan 2021

See all articles by Battal Doğan

Battal Doğan

Department of Economics, University of Bristol

Lars Ehlers

University of Montreal - Département de Sciences Economiques and CIREQ

Date Written: January 8, 2021

Abstract

We investigate efficient and minimally unstable Pareto improvements over the deferred acceptance (DA) mechanism — a popular school choice mechanism which is stable but not efficient. We show that there is no Pareto improvement over the DA mechanism which is minimally unstable among efficient assignments when the stability comparison is based on counting the number of blocking pairs. Our main result characterizes the priority profiles for which there exists a Pareto improvement over the DA assignment that is minimally unstable among efficient assignments. We further consider an alternative natural stability comparison based on the set of blocking students who are involved in at least one blocking pair, show that the impossibilities remain, and characterize the possibility domain of priority profiles.

Keywords: school choice, deferred acceptance, stability comparisons, cardinal minimal instability

JEL Classification: C70, D47, D61, D63

Suggested Citation

Doğan, Battal and Ehlers, Lars, Minimally Unstable Pareto Improvements over Deferred Acceptance (January 8, 2021). Available at SSRN: https://ssrn.com/abstract=3697844 or http://dx.doi.org/10.2139/ssrn.3697844

Battal Doğan (Contact Author)

Department of Economics, University of Bristol ( email )

United Kingdom

Lars Ehlers

University of Montreal - Département de Sciences Economiques and CIREQ ( email )

C.P. 6128, succursale Centre-Ville
Montreal, Quebec H3C 3J7
Canada

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