The Median Rule in Judgement Aggregation

40 Pages Posted: 10 Feb 2018

See all articles by Klaus Nehring

Klaus Nehring

University of California, Davis - Department of Economics

Marcus Pivato

THEMA, CY Cergy Paris Université

Date Written: January 30, 2018

Abstract

A judgement aggregation rule takes the views of a collection of voters over a set of interconected issues, and yields a logically consistent collective view. The median rule is a judgement aggregation rule that selects the logically consistent view which minimizes the average distance to the views of the voters (where the “distance” between two views is the number of issues on which they disagree). In the special case of preference aggregation, this is called the Kemeny rule. We show that, under appropriate regularity conditions, the median rule is the unique judgement aggregation rule which satisfies three axioms: Ensemble Supermajority Efficiency, Reinforcement, and Continuity. Our analysis covers aggregation problems in which different issues have different weights, and in which the consistency restrictions on input and output judgments may differ.

Keywords: Judgement Aggregation, Majoritarian, Reinforcement, Consistency, Median

JEL Classification: D71

Suggested Citation

Nehring, Klaus and Pivato, Marcus, The Median Rule in Judgement Aggregation (January 30, 2018). Available at SSRN: https://ssrn.com/abstract=3113562 or http://dx.doi.org/10.2139/ssrn.3113562

Klaus Nehring

University of California, Davis - Department of Economics ( email )

One Shields Drive
Davis, CA 95616-8578
United States
916-752-3379 (Phone)
916-752-9382 (Fax)

Marcus Pivato (Contact Author)

THEMA, CY Cergy Paris Université ( email )

33 Boulevard du Port
Cergy-Pontoise Cedex, Cedex 95011
France

HOME PAGE: http://https://sites.google.com/site/marcuspivato/

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