A Generalised Theory of Proportionality in Collective Decision Making

Fuente: arXiv
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Main Authors: Masařík, Tomáš, Pierczyński, Grzegorz, Skowron, Piotr
Format: Preprint
Published: 2023
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author Masařík, Tomáš
Pierczyński, Grzegorz
Skowron, Piotr
author_facet Masařík, Tomáš
Pierczyński, Grzegorz
Skowron, Piotr
contents We consider a voting model, where a number of candidates need to be selected subject to certain feasibility constraints. The model generalises committee elections (where there is a single constraint on the number of candidates that need to be selected), various elections with diversity constraints, the model of public decisions (where decisions needs to be taken on a number of independent issues), and the model of collective scheduling. A critical property of voting is that it should be fair -- not only to individuals but also to groups of voters with similar opinions on the subject of the vote; in other words, the outcome of an election should proportionally reflect the voters' preferences. We formulate axioms of proportionality in this general model. Our axioms do not require predefining groups of voters; to the contrary, we ensure that the opinion of every subset of voters whose preferences are cohesive-enough are taken into account to the extent that is proportional to the size of the subset. Our axioms generalise the strongest known satisfiable axioms for the more specific models. We explain how to adapt two prominent committee election rules, Proportional Approval Voting (PAV) and Phragmén Sequential Rule, as well as the concept of stable-priceability to our general model. The two rules satisfy our proportionality axioms if and only if the feasibility constraints are matroids.
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id arxiv_https___arxiv_org_abs_2307_06077
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle A Generalised Theory of Proportionality in Collective Decision Making
Masařík, Tomáš
Pierczyński, Grzegorz
Skowron, Piotr
Computer Science and Game Theory
Multiagent Systems
We consider a voting model, where a number of candidates need to be selected subject to certain feasibility constraints. The model generalises committee elections (where there is a single constraint on the number of candidates that need to be selected), various elections with diversity constraints, the model of public decisions (where decisions needs to be taken on a number of independent issues), and the model of collective scheduling. A critical property of voting is that it should be fair -- not only to individuals but also to groups of voters with similar opinions on the subject of the vote; in other words, the outcome of an election should proportionally reflect the voters' preferences. We formulate axioms of proportionality in this general model. Our axioms do not require predefining groups of voters; to the contrary, we ensure that the opinion of every subset of voters whose preferences are cohesive-enough are taken into account to the extent that is proportional to the size of the subset. Our axioms generalise the strongest known satisfiable axioms for the more specific models. We explain how to adapt two prominent committee election rules, Proportional Approval Voting (PAV) and Phragmén Sequential Rule, as well as the concept of stable-priceability to our general model. The two rules satisfy our proportionality axioms if and only if the feasibility constraints are matroids.
title A Generalised Theory of Proportionality in Collective Decision Making
topic Computer Science and Game Theory
Multiagent Systems
url https://arxiv.org/abs/2307.06077