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arXiv · 2305.04589

First-Choice Maximality Meets Ex-ante and Ex-post Fairness

Xiaoxi Guo·Sujoy Sikdar·Lirong Xia·Yongzhi Cao·Hanpin Wang
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Abstract

For the assignment problem where multiple indivisible items are allocated to a group of agents given their ordinal preferences, we design randomized mechanisms that satisfy first-choice maximality (FCM), i.e., maximizing the number of agents assigned their first choices, together with Pareto efficiency (PE). Our mechanisms also provide guarantees of ex-ante and ex-post fairness. The generalized eager Boston mechanism is ex-ante envy-free, and ex-post envy-free up to one item (EF1). The generalized probabilistic Boston mechanism is also ex-post EF1, and satisfies ex-ante efficiency instead of fairness. We also show that no strategyproof mechanism satisfies ex-post PE, EF1, and FCM simultaneously. In doing so, we expand the frontiers of simultaneously providing efficiency and both ex-ante and ex-post fairness guarantees for the assignment problem.

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Xiaoxi Guo, Sujoy Sikdar, Lirong Xia, Yongzhi Cao, Hanpin Wang. 2023-05-08. First-Choice Maximality Meets Ex-ante and Ex-post Fairness. https://arxiv.org/abs/2305.04589

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