Duverger's Law in mixed legislative systems: The impact of national electoral rules on district competition

Abstract

AbstractHow do institutional factors shape district competition in mixed legislative systems? Preliminary evidence suggests the distinction between sub‐types of mixed systems alone poorly explains variation in district results. Consistent with the contamination thesis, this analysis suggests three additional national‐level factors at play: fused ballots, the electoral threshold for proportional representation seats, and the existence of compulsory voting laws. Regression analysis on an original dataset covering 90 mixed system elections in 23 countries (1990–2012) finds that while mixed member majoritarian systems correlate with fewer district candidates, these three often overlooked factors are also statistically significant. This analysis highlights the complexity of mixed systems and suggests why many of them diverge from Duverger's Law.