Compatible $k$-Relaxations of Fairness and Non-Wastefulness Under Hereditary Constraints

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Main Authors: Wakasugi, Tenma, Sun, Zhaohong, Kimura, Kei, Yokoo, Makoto
Format: Preprint
Published: 2026
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author Wakasugi, Tenma
Sun, Zhaohong
Kimura, Kei
Yokoo, Makoto
author_facet Wakasugi, Tenma
Sun, Zhaohong
Kimura, Kei
Yokoo, Makoto
contents We study two-sided matching markets under hereditary constraints, which extend beyond simple capacity limits and arise in applications such as diversity requirements and refugee resettlement. In these settings, fairness and non-wastefulness are often incompatible, and existing approaches typically address this tension by prioritizing one property at the expense of the other. We take a different approach by relaxing both properties simultaneously in a controlled and symmetric manner. We introduce two notions indexed by an integer $k$: envy-received up to $k$ peers (ER-$k$) and non-wastefulness up to $k$ objections (NW-$k$). Our main theoretical result shows that ER-$k$ and NW-$k$ are always compatible under hereditary constraints for any fixed $k$. We provide two equivalent polynomial-time algorithms to compute such matchings: a $k$-admissible cutoff algorithm and a $k$-admissible college-proposing deferred acceptance mechanism. Finally, experimental results demonstrate that even small relaxations achieve a favorable balance between fairness and non-wastefulness.
format Preprint
id arxiv_https___arxiv_org_abs_2605_00134
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Compatible $k$-Relaxations of Fairness and Non-Wastefulness Under Hereditary Constraints
Wakasugi, Tenma
Sun, Zhaohong
Kimura, Kei
Yokoo, Makoto
Computer Science and Game Theory
91B68
F.2; I.2
We study two-sided matching markets under hereditary constraints, which extend beyond simple capacity limits and arise in applications such as diversity requirements and refugee resettlement. In these settings, fairness and non-wastefulness are often incompatible, and existing approaches typically address this tension by prioritizing one property at the expense of the other. We take a different approach by relaxing both properties simultaneously in a controlled and symmetric manner. We introduce two notions indexed by an integer $k$: envy-received up to $k$ peers (ER-$k$) and non-wastefulness up to $k$ objections (NW-$k$). Our main theoretical result shows that ER-$k$ and NW-$k$ are always compatible under hereditary constraints for any fixed $k$. We provide two equivalent polynomial-time algorithms to compute such matchings: a $k$-admissible cutoff algorithm and a $k$-admissible college-proposing deferred acceptance mechanism. Finally, experimental results demonstrate that even small relaxations achieve a favorable balance between fairness and non-wastefulness.
title Compatible $k$-Relaxations of Fairness and Non-Wastefulness Under Hereditary Constraints
topic Computer Science and Game Theory
91B68
F.2; I.2
url https://arxiv.org/abs/2605.00134