Climbers and Divers: Self‑Primacy Effects in Open‑List Proportional Representation

This article investigates list primacy in open-list proportional representation (OLPR) using a new “climbers and divers” design that compares the same candidates’ vote shares when they appear at the top versus lower on their party list in consecutive Polish local elections from 2006–2022. By tracking candidates who move up (climbers) or down (divers) between elections, and modeling their within-list vote shares conditional on party performance, district magnitude, list length, and basic demographic context, the study isolates a self-primacy effect net of many confounders associated with list construction. The results show a substantial, two-digit percentage-point bonus for top-listed candidates, with somewhat weaker but still large effects in the most numerous county races, indicating that list position is a major source of intra-party inequality even among otherwise similar co-partisans. The article concludes by discussing the limits of the climbers–divers strategy, the non-random nature of list movements, and policy options for mitigating list primacy in OLPR.