---
title: "Group-Strategyproof Irresolute Social Choice Functions"
authors:
  - "Felix Brandt"
doi: "10.5591/978-1-57735-516-8/IJCAI11-025"
url: "https://ijcai.org/proceedings/2011/25"
pdf: "https://ijcai.org/proceedings/2011/0025.pdf"
venue: "Proceedings of the Twenty-Second International Joint Conference on Artificial Intelligence"
year: 2011
pages: "79-83"
track: ""
keywords:
---

# Group-Strategyproof Irresolute Social Choice Functions

Felix Brandt

*Proceedings of the Twenty-Second International Joint Conference on Artificial Intelligence*, pages 79-83. DOI: [10.5591/978-1-57735-516-8/IJCAI11-025](https://doi.org/10.5591/978-1-57735-516-8/IJCAI11-025)

## Abstract

An important problem in voting is that agents may misrepresent their preferences in order to obtain a more preferred outcome. Unfortunately, this phenomenon has been shown to be inevitable in the case of resolute, i.e., single-valued, social choice functions. In this paper, we introduce a variant of Maskin-monotonicity that completely characterizes the class of pairwise irresolute social choice functions that are group-strategyproof according to Kelly's preference extension.The class is narrow but contains a number of appealing Condorcet extensions such as the minimal covering set and the bipartisan set, thereby answering a question raised independently by Barbera (1977) and Kelly (1977). These functions furthermore encourage participation and thus do not suffer from the no-show paradox (under Kelly's extension).