---
title: "The Proportional Veto Principle for Approval Ballots"
authors:
  - "Daniel Halpern"
  - "Ariel D. Procaccia"
  - "Warut Suksompong"
doi: "10.24963/ijcai.2025/434"
url: "https://ijcai.org/proceedings/2025/434"
pdf: "https://ijcai.org/proceedings/2025/0434.pdf"
venue: "Proceedings of the Thirty-Fourth International Joint Conference on Artificial Intelligence"
year: 2025
pages: "3900-3907"
track: "Main Track"
keywords:
  - "Game Theory and Economic Paradigms: GTEP: Computational social choice"
---

# The Proportional Veto Principle for Approval Ballots

Daniel Halpern, Ariel D. Procaccia, Warut Suksompong

*Proceedings of the Thirty-Fourth International Joint Conference on Artificial Intelligence*, pages 3900-3907. DOI: [10.24963/ijcai.2025/434](https://doi.org/10.24963/ijcai.2025/434)

## Abstract

The proportional veto principle, which captures the idea that a candidate vetoed by a large group of voters should not be chosen, has been studied for ranked ballots in single-winner voting. We introduce a version of this principle for approval ballots, which we call flexible-voter representation (FVR). We show that while the approval voting rule and other natural scoring rules provide the optimal FVR guarantee only for some flexibility threshold, there exists a scoring rule that is FVR-optimal for all thresholds simultaneously. We also extend our results to multi-winner voting.