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arXiv · 2508.05340

Pairwise efficiency and monotonicity imply Pareto efficiency in (probabilistic) object allocation

Tom Demeulemeester·Bettina Klaus
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Abstract

We consider object allocation problems with capacities where objects have to be assigned to agents. We show that a probabilistically monotonic lottery rule satisfies ex-post Pareto efficiency if and only if it satisfies ex-post pairwise efficiency and ex-post nonwastefulness. This result allows us to strengthen various existing characterization results, both for lottery rules and for deterministic rules, by replacing (ex-post) Pareto efficiency with (ex-post) pairwise efficiency and (ex-post) non-wastefulness, e.g., for characterizations of the Random Serial Dictatorship rule (Basteck, 2025), Trading Cycles rules (Pycia and Unver, 2017), and Hierarchical Exchange rules (Papai, 2000).

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Tom Demeulemeester, Bettina Klaus. 2025-08-07. Pairwise efficiency and monotonicity imply Pareto efficiency in (probabilistic) object allocation. https://arxiv.org/abs/2508.05340

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