Distance rationalization of social rules

TL;DR

This paper advances the theoretical understanding of distance rationalizability in social choice rules by addressing foundational questions, correcting previous work, and connecting the framework with geometric concepts like Earth Mover distance.

Contribution

It unifies and generalizes prior research, introduces new results on uniqueness, and improves conditions for desirable properties in distance rationalized rules.

Findings

Counterexample for uniqueness of representation.

Compression of profile representations via quotient constructions.

Enhanced conditions ensuring well-behaved rationalized rules.

Abstract

The concept of distance rationalizability of social choice rules has been explored in recent years by several authors. We deal here with several foundational questions, and unify, correct, and generalize previous work. For example, we study a new question involving uniqueness of representation in the distance rationalizability framework, and present a counterexample. For rules satisfying various axiomatic properties such as anonymity, neutrality and homogeneity, the standard profile representation of input can be compressed substantially. We explain in detail using quotient constructions and symmetry groups how distance rationalizability is interpreted in this situation. This enables us to connect the theory of distance rationalizability with geometric concepts such as Earth Mover distance and optimal transportation. We expect this connection to prove fruitful in future work. We improve on the best-known sufficient conditions for rules rationalized via votewise distances to satisfy anonymity, neutrality, homogeneity, consistency and continuity. This leads to a class of well-behaved rules which deserve closer scrutiny in future.