Blocking Pairs Versus Blocking Students: Stability Comparisons in School Choice

Doğan, Battal; Ehlers, Lars

doi:10.2139/ssrn.3571173

Cited by 6 publications

(3 citation statements)

References 15 publications

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“…Among the Pareto efficient mechanisms, the most fair by stability is the Efficiencyadjusted Deferred Acceptance mechanism (EADA) due to Kesten (2010) -both in terms of blocking pairs and blocking triplets (Dogan and Ehlers, 2020a;Tang and Zhang, 2020;Kwon and Shorrer, 2019). Independent from the present work, Dogan and Ehlers (2020a) also use the fairness by counting criterion to show that among efficient mechanisms EADA is not the most fair by counting, unless the priority profile satisfies few acyclicity conditions.…”

Section: Introductionmentioning

confidence: 90%

Reforms meet fairness concerns in school and college admissions

Bonkoungou¹,

Nesterov²

2020

Preprint

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Recently, many matching systems around the world have been reformed. These reforms responded to objections that the matching mechanisms in use were unfair and manipulable. Surprisingly, the mechanisms remained unfair even after the reforms: the new mechanisms may induce an outcome with a blocking student who desires and deserves a school which she did not receive.However, as we show in this paper, the reforms introduced matching mechanisms which are more fair compared to the counterfactuals. First, most of the reforms introduced mechanisms that are more fair by stability: whenever the old mechanism does not have a blocking student, the new mechanism does not have a blocking student either. Second, some reforms introduced mechanisms that are more fair by counting: the old mechanism always has at least as many blocking students as the new mechanism.These findings give a novel rationale to the reforms and complement the recent literature showing that the same reforms have introduced less manipulable matching mechanisms. We further show that the fairness and manipulability of the mechanisms are strongly logically related.

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Section: Introductionmentioning

confidence: 90%

Reforms meet fairness concerns in school and college admissions

Bonkoungou¹,

Nesterov²

2020

Preprint

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“…The proof of Theorem 2 is similar to the proof of Theorem 1 and is available in Doğan and Ehlers (2020a).…”

Section: Stability Comparisons Based On Blocking Studentsmentioning

confidence: 99%

Minimally unstable Pareto improvements over deferred acceptance

Doğan¹,

Ehlers

2021

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We investigate efficient and minimally unstable Pareto improvements over the deferred acceptance (DA) mechanism—a popular school choice mechanism that is stable but not efficient. We show that there is no Pareto improvement over the DA mechanism that 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.

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“…The proof of Theorem 2 is similar to the proof of Theorem 1 and is available in Dogan and Ehlers (2020a).…”

Section: Stability Comparisons Based On Blocking Studentsmentioning

confidence: 99%