Polity size and women’s representation: evidence from two large-scale boundary reforms

Do larger polities hinder gender parity in elected office? We theorize that when populations grow faster than elected assemblies, a “seat congestion” effect intensifies competition for nominations, enabling men candidates to crowd out women. We test this argument using two nationwide natural experiments: Swedish municipal amalgamations in 1952 and 1973 that abruptly increased electorates. We track the effects in newly digitized historical panel data. Where electorate-per-seat ratios rose, growth in women’s representation slowed. Decomposition analyses show that expanding councils only partially offsets congestion. By identifying polity size as a systematic brake on descriptive representation, the study adds a demographic dimension to debates on institutional design and points to an overlooked cost of increasing jurisdictional size.