Fair Lotteries for Participatory Budgeting

Fuente: arXiv
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Auteurs principaux: Aziz, Haris, Lu, Xinhang, Suzuki, Mashbat, Vollen, Jeremy, Walsh, Toby
Format: Preprint
Publié: 2024
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author Aziz, Haris
Lu, Xinhang
Suzuki, Mashbat
Vollen, Jeremy
Walsh, Toby
author_facet Aziz, Haris
Lu, Xinhang
Suzuki, Mashbat
Vollen, Jeremy
Walsh, Toby
contents In pursuit of participatory budgeting (PB) outcomes with broader fairness guarantees, we initiate the study of lotteries over discrete PB outcomes. As the projects have heterogeneous costs, the amount spent may not be equal ex ante and ex post. To address this, we develop a technique to bound the amount by which the ex-post spend differs from the ex-ante spend -- the property is termed budget balanced up to one project (BB1). With respect to fairness, we take a best-of-both-worlds perspective, seeking outcomes that are both ex-ante and ex-post fair. Towards this goal, we initiate a study of ex-ante fairness properties in PB, including Individual Fair Share (IFS), Unanimous Fair Share (UFS) and their stronger variants, as well as Group Fair Share (GFS). We show several incompatibility results between these ex-ante fairness notions and existing ex-post concepts based on justified representation. One of our main contributions is a randomized algorithm which simultaneously satisfies ex-ante Strong UFS, ex-post full justified representation (FJR) and ex-post BB1 for PB with binary utilities.
format Preprint
id arxiv_https___arxiv_org_abs_2404_05198
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Fair Lotteries for Participatory Budgeting
Aziz, Haris
Lu, Xinhang
Suzuki, Mashbat
Vollen, Jeremy
Walsh, Toby
Computer Science and Game Theory
In pursuit of participatory budgeting (PB) outcomes with broader fairness guarantees, we initiate the study of lotteries over discrete PB outcomes. As the projects have heterogeneous costs, the amount spent may not be equal ex ante and ex post. To address this, we develop a technique to bound the amount by which the ex-post spend differs from the ex-ante spend -- the property is termed budget balanced up to one project (BB1). With respect to fairness, we take a best-of-both-worlds perspective, seeking outcomes that are both ex-ante and ex-post fair. Towards this goal, we initiate a study of ex-ante fairness properties in PB, including Individual Fair Share (IFS), Unanimous Fair Share (UFS) and their stronger variants, as well as Group Fair Share (GFS). We show several incompatibility results between these ex-ante fairness notions and existing ex-post concepts based on justified representation. One of our main contributions is a randomized algorithm which simultaneously satisfies ex-ante Strong UFS, ex-post full justified representation (FJR) and ex-post BB1 for PB with binary utilities.
title Fair Lotteries for Participatory Budgeting
topic Computer Science and Game Theory
url https://arxiv.org/abs/2404.05198