Reallocating Wasted Votes in Proportional Parliamentary Elections with Thresholds

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).

@article{delemazure2025_2503.17156,
  title={ Reallocating Wasted Votes in Proportional Parliamentary Elections with Thresholds },
  author={ Théo Delemazure and Rupert Freeman and Jérôme Lang and Jean-François Laslier and Dominik Peters },
  journal={arXiv preprint arXiv:2503.17156},
  year={ 2025 }
}