Properties of Multiwinner Voting Rules

TL;DR

This paper analyzes properties of various multiwinner voting rules, generalizing single-winner scoring rules, and evaluates their adherence to desirable criteria to understand their behavior and effectiveness.

Contribution

It introduces a framework for classifying multiwinner rules into two natural classes and evaluates several existing rules against proposed desirable properties.

Findings

Many rules fit into the two identified classes.

Some rules satisfy most desirable properties.

The framework helps compare and understand multiwinner voting rules.

Abstract

The goal of this paper is to propose and study properties of multiwinner voting rules which can be consider as generalisations of single-winner scoring voting rules. We consider SNTV, Bloc, k-Borda, STV, and several variants of Chamberlin--Courant's and Monroe's rules and their approximations. We identify two broad natural classes of multiwinner score-based rules, and show that many of the existing rules can be captured by one or both of these approaches. We then formulate a number of desirable properties of multiwinner rules, and evaluate the rules we consider with respect to these properties.