Can a Few Decide for Many? The Metric Distortion of Sortition

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Main Authors: Caragiannis, Ioannis, Micha, Evi, Peters, Jannik
Format: Preprint
Published: 2024
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author Caragiannis, Ioannis
Micha, Evi
Peters, Jannik
author_facet Caragiannis, Ioannis
Micha, Evi
Peters, Jannik
contents Recent works have studied the design of algorithms for selecting representative sortition panels. However, the most central question remains unaddressed: Do these panels reflect the entire population's opinion? We present a positive answer by adopting the concept of metric distortion from computational social choice, which aims to quantify how much a panel's decision aligns with the ideal decision of the population when preferences and agents lie on a metric space. We show that uniform selection needs only logarithmically many agents in terms of the number of alternatives to achieve almost optimal distortion. We also show that Fair Greedy Capture, a selection algorithm introduced recently by Ebadian & Micha (2024), matches uniform selection's guarantees of almost optimal distortion and also achieves constant ex-post distortion, ensuring a "best of both worlds" performance.
format Preprint
id arxiv_https___arxiv_org_abs_2406_02400
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Can a Few Decide for Many? The Metric Distortion of Sortition
Caragiannis, Ioannis
Micha, Evi
Peters, Jannik
Computer Science and Game Theory
Recent works have studied the design of algorithms for selecting representative sortition panels. However, the most central question remains unaddressed: Do these panels reflect the entire population's opinion? We present a positive answer by adopting the concept of metric distortion from computational social choice, which aims to quantify how much a panel's decision aligns with the ideal decision of the population when preferences and agents lie on a metric space. We show that uniform selection needs only logarithmically many agents in terms of the number of alternatives to achieve almost optimal distortion. We also show that Fair Greedy Capture, a selection algorithm introduced recently by Ebadian & Micha (2024), matches uniform selection's guarantees of almost optimal distortion and also achieves constant ex-post distortion, ensuring a "best of both worlds" performance.
title Can a Few Decide for Many? The Metric Distortion of Sortition
topic Computer Science and Game Theory
url https://arxiv.org/abs/2406.02400