Reallocating Wasted Votes in Proportional Parliamentary Elections with Thresholds

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Main Authors: Delemazure, Théo, Freeman, Rupert, Lang, Jérôme, Laslier, Jean-François, Peters, Dominik
Format: Preprint
Published: 2025
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author Delemazure, Théo
Freeman, Rupert
Lang, Jérôme
Laslier, Jean-François
Peters, Dominik
author_facet Delemazure, Théo
Freeman, Rupert
Lang, Jérôme
Laslier, Jean-François
Peters, Dominik
contents In many proportional parliamentary elections, electoral thresholds (typically 3-5%) are used to promote stability and governability by preventing the election of parties with very small representation. However, these thresholds often result in a significant number of "wasted votes" cast for parties that fail to meet the threshold, which reduces representativeness. One proposal is to allow voters to specify replacement votes, by either indicating a second choice party or by ranking a subset of the parties, but there are several ways of deciding on the scores of the parties (and thus the composition of the parliament) given those votes. We introduce a formal model of party voting with thresholds, and compare a variety of party selection rules axiomatically, and experimentally using a dataset we collected during the 2024 European election in France. We identify three particularly attractive rules, called Direct Winners Only (DO), Single Transferable Vote (STV) and Greedy Plurality (GP).
format Preprint
id arxiv_https___arxiv_org_abs_2503_17156
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Reallocating Wasted Votes in Proportional Parliamentary Elections with Thresholds
Delemazure, Théo
Freeman, Rupert
Lang, Jérôme
Laslier, Jean-François
Peters, Dominik
Computer Science and Game Theory
Theoretical Economics
In many proportional parliamentary elections, electoral thresholds (typically 3-5%) are used to promote stability and governability by preventing the election of parties with very small representation. However, these thresholds often result in a significant number of "wasted votes" cast for parties that fail to meet the threshold, which reduces representativeness. One proposal is to allow voters to specify replacement votes, by either indicating a second choice party or by ranking a subset of the parties, but there are several ways of deciding on the scores of the parties (and thus the composition of the parliament) given those votes. We introduce a formal model of party voting with thresholds, and compare a variety of party selection rules axiomatically, and experimentally using a dataset we collected during the 2024 European election in France. We identify three particularly attractive rules, called Direct Winners Only (DO), Single Transferable Vote (STV) and Greedy Plurality (GP).
title Reallocating Wasted Votes in Proportional Parliamentary Elections with Thresholds
topic Computer Science and Game Theory
Theoretical Economics
url https://arxiv.org/abs/2503.17156