# Ties in Multiwinner Approval Voting

arXiv: https://arxiv.org/abs/2305.01769 · HTML: https://mlsanity.com/paper/2305.01769/

## Key facts

- Cited by 3 papers in the map (data through 14 Oct 2026).
- First posted on arXiv 2 May 2023.

## Built on by (most cited first, 3 of 3)

- [Multiwinner Temporal Voting with Aversion to Change](https://mlsanity.com/paper/2408.11017/) (2024)
- [Learning Aggregation Rules in Participatory Budgeting: A Data-Driven Approach](https://mlsanity.com/paper/2412.01864/) (2024)
- [Reverse Sequential Proportional Approval Voting Rule: Proportionality and Approximation Guarantees](https://mlsanity.com/paper/2609.35331/) (2026)

## Abstract (arXiv)

We study the complexity of deciding whether there is a tie in a given approval-based multiwinner election, as well as the complexity of counting tied winning committees. We consider a family of Thiele rules, their greedy variants, Phragmen's sequential rule, and Method of Equal Shares. For most cases, our problems are computationally hard, but for sequential rules we find an FPT algorithm for discovering ties (parameterized by the committee size). We also show experimentally that in elections of moderate size ties are quite frequent.