Compromising on compromise rules

Barberà, Salvador; Coelho, Danilo Santa Cruz

doi:10.1111/1756-2171.12401

Cited by 12 publications

(6 citation statements)

References 24 publications

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“…Looking at the sequential mechanisms in the literature, we can start with the Rule of k names proposed by Barberà and Coelho (2010). In the Rule of k names, one of the parties proposes a shortlist, and the other chooses from it (Barberà and Coelho 2022). Then a single individual from outside the committee selects one of the listed names for the office.…”

Section: Literature Reviewmentioning

confidence: 99%

“…Then a single individual from outside the committee selects one of the listed names for the office. Later, Barberà and Coelho (2022) proposed three mechanisms based on the Rule of k names. The characteristics of these mechanisms are that they contain few steps, weakly implement the Unanimity Compromise Set, and are robust to the strategic inclusion of candidates.…”

Section: Literature Reviewmentioning

confidence: 99%

“…A mechanism from the Rule of k names family has not been compared with the Shortlisting mechanism before. Therefore, we included the Alternate Shortlisting and Compromise Rule of k Names mechanisms proposed by Barberà and Coelho (2022) in the analysis. Although Shortlisting mechanism and Gradual Veto have been compared before, this comparison is incomplete in some respects; for example, it does not include an Equal Loss Principle analysis.…”

Section: Literature Reviewmentioning

confidence: 99%

See 2 more Smart Citations

An Experiment on Two-Person Social Choice

Bas¹

2023

AEA Randomized Controlled Trials

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Section: Literature Reviewmentioning

confidence: 99%

Section: Literature Reviewmentioning

confidence: 99%

Section: Literature Reviewmentioning

confidence: 99%

See 1 more Smart Citation

An Experiment on Two-Person Social Choice

Bas¹

2023

AEA Randomized Controlled Trials

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“…Given that we can compute the veto core in polynomial time, however, one could suggest any number of neutral and anonymous core selection algorithms -first compute the veto core, throw away all other candidates, and use your favourite voting rule to select a winner from what is left. Unfortunately, the veto core is vulnerable to a very simple form of agenda manipulation -padding the profile at the bottom with universally reviled candidates (Kondratev, Ianovski, and Nesterov 2019;Barberà and Coelho 2020). Indeed, suppose we add (n − 1)m spoiler candidates at the bottom of every voter's preference order.…”

Section: Selecting From the Veto Corementioning

confidence: 99%

Computing the Proportional Veto Core

Ianovski¹,

Kondratev²

2021

AAAI

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In social choice there often arises a conflict between the majority principle (the search for a candidate that is as good as possible for as many voters as possible), and the protection of minority rights (choosing a candidate that is not overly bad for particular individuals or groups). In a context where the latter is our main concern, veto-based rules -- giving individuals or groups the ability to strike off certain candidates from the list -- are a natural and effective way of ensuring that no minority is left with an outcome they find untenable. However, such rules often fail to be anonymous, or impose specific restrictions on the number of voters and candidates. These issues can be addressed by considering the proportional veto core -- the solution to a cooperative game where every coalition is given the power to veto a number of candidates proportional to its size. However, the naive algorithm for the veto core is exponential, and the only known rules for selecting from the veto core, with an arbitrary number of voters, violate either anonymity or neutrality. In this paper we present a polynomial time algorithm for computing the veto core and present a neutral and anonymous algorithm for selecting a candidate from it. We also show that a pessimist can manipulate the veto core in polynomial time.

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“…Arbitration rules are thoroughly discussed by Barberà and Coelho (2020). As prominent examples, we have fallback bargaining proposed by Brams and Kilgour (2001), the veto-rank and short listing procedures analysed by de Clippel et al (2014) and the Pareto-and-veto rules analysed by Laslier et al (2020).…”

Section: Introductionmentioning

confidence: 99%

Compromising as an equal loss principle

2022

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A social choice rule aggregates the preferences of a group of individuals over a set of alternatives into a collective choice. The literature admits several social choice rules whose recommendations are supposed to reflect a compromise among individuals. We observe that all these compromise rules can be better described as procedural compromises, i.e., they impose over individuals a willingness to compromise but they do not ensure an outcome where everyone has effectively compromised. We revisit the concept of a compromise in a collective choice environment with at least three individuals having strict preferences over a finite set of alternatives. Referring to a large class of spread measures, we view the concept of compromise from an equal loss perspective, favoring an outcome where every voter concedes as equally as possible. As such, being a compromise may fail Pareto efficiency, which we ensure by asking voters to concede as equally as possible among the Pareto efficient alternatives. We show that Condorcet consistent rules, scoring rules (except antiplurality) and Brams-Kilgour compromises (except fallback bargaining) all fail to ascertain an outcome which is a compromise. A slight restriction on acceptable spread measures suffices to extend the negative result to antiplurality and fallback bargaining. This failure also prevails for social choice problems with two individuals: all well-known two-person social choice rules of the literature, namely, fallback bargaining, Pareto and veto rules, short listing and veto rank, fail to pick ex-post compromises. We conclude that there is a need to propose and study rules that satisfy this equal loss, or outcome oriented, notion of a compromise.

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Compromising on compromise rules

Cited by 12 publications

References 24 publications

An Experiment on Two-Person Social Choice

An Experiment on Two-Person Social Choice

Computing the Proportional Veto Core

Compromising as an equal loss principle

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