An axiomatic derivation of Condorcet-consistent social decision rules

TL;DR

This paper provides an axiomatic characterization of Condorcet-consistent social decision rules, highlighting their properties and differences from scoring rules, and introduces concepts like top consistency and Maskin monotonicity.

Contribution

It offers a novel set of axioms characterizing Condorcet-consistent rules and distinguishes them from scoring rules using top consistency and Maskin monotonicity.

Findings

All Condorcet-consistent SDRs satisfy top consistency.

Scoring rules do not satisfy top consistency.

Axiomatic characterization via minimal axioms and Maskin monotonicity.

Abstract

A social decision rule (SDR) is any non-empty set-valued map that associates any profile of individual preferences with the set of (winning) alternatives. An SDR is Condorcet-consistent if it selects the set of Condorcet winners whenever this later is non-empty. We propose a characterization of Condorcet consistent SDRs with a set of minimal axioms. It appears that all these rules satisfy a weaker Condorcet principle - the top consistency - which is not explicitly based on majority comparisons while all scoring rules fail to meet it. We also propose an alternative characterization of this class of rules using Maskin monotonicity.