TY - JOUR

T1 - Plurality in Spatial Voting Games with Constant β

AU - Filtser, Arnold

AU - Filtser, Omrit

N1 - Publisher Copyright:
© 2024, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.

PY - 2024/1/3

Y1 - 2024/1/3

N2 - Consider a set V of voters, represented by a multiset in a metric space (X, d). The voters have to reach a decision—a point in X. A choice p∈ X is called a β -plurality point for V, if for any other choice q∈ X it holds that |{v∈V∣β·d(p,v)≤d(q,v)}|≥|V|2 . In other words, at least half of the voters “prefer” p over q, when an extra factor of β is taken in favor of p. For β= 1 , this is equivalent to Condorcet winner, which rarely exists. The concept of β -plurality was suggested by Aronov, de Berg, Gudmundsson, and Horton [TALG 2021] as a relaxation of the Condorcet criterion. Let β(X,d)∗=sup{β∣everyfinitemultisetVinXadmitsaβ-pluralitypoint} . The parameter β∗ determines the amount of relaxation required in order to reach a stable decision. Aronov et al. showed that for the Euclidean plane β(R2,‖·‖2)∗=32 , and more generally, for d-dimensional Euclidean space, 1d≤β(Rd,‖·‖2)∗≤32 . In this paper, we show that 0.557≤β(Rd,‖·‖2)∗ for any dimension d (notice that 1d<0.557 for any d≥ 4). In addition, we prove that for every metric space (X, d) it holds that 2-1≤β(X,d)∗ , and show that there exists a metric space for which β(X,d)∗≤12 .

AB - Consider a set V of voters, represented by a multiset in a metric space (X, d). The voters have to reach a decision—a point in X. A choice p∈ X is called a β -plurality point for V, if for any other choice q∈ X it holds that |{v∈V∣β·d(p,v)≤d(q,v)}|≥|V|2 . In other words, at least half of the voters “prefer” p over q, when an extra factor of β is taken in favor of p. For β= 1 , this is equivalent to Condorcet winner, which rarely exists. The concept of β -plurality was suggested by Aronov, de Berg, Gudmundsson, and Horton [TALG 2021] as a relaxation of the Condorcet criterion. Let β(X,d)∗=sup{β∣everyfinitemultisetVinXadmitsaβ-pluralitypoint} . The parameter β∗ determines the amount of relaxation required in order to reach a stable decision. Aronov et al. showed that for the Euclidean plane β(R2,‖·‖2)∗=32 , and more generally, for d-dimensional Euclidean space, 1d≤β(Rd,‖·‖2)∗≤32 . In this paper, we show that 0.557≤β(Rd,‖·‖2)∗ for any dimension d (notice that 1d<0.557 for any d≥ 4). In addition, we prove that for every metric space (X, d) it holds that 2-1≤β(X,d)∗ , and show that there exists a metric space for which β(X,d)∗≤12 .

KW - Condorcet criterion

KW - Plurality points

KW - Social choice

UR - http://www.scopus.com/inward/record.url?scp=85181250469&partnerID=8YFLogxK

U2 - 10.1007/s00454-023-00619-5

DO - 10.1007/s00454-023-00619-5

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AN - SCOPUS:85181250469

SN - 0179-5376

JO - Discrete and Computational Geometry

JF - Discrete and Computational Geometry

ER -