Looking for the Magic Number: The Optimal District Magnitude for Political Parties in d'Hondt PR and SNTV

In: Electoral Studies, Band 22, Heft 1, S. 49-63

Abstract

District magnitude is regarded by many as the principal dimension that spans the classification of electoral systems. It is believed that larger parties prefer smaller district magnitudes & vice versa. Problems arise when one tries to be exact: how large must a party be for the single-member district system to be its most favorable choice? Will any party find a particular magnitude most preferable? This article extends existing theories of effective thresholds & proposes a seat-vote equation different from the cube law. With reasonable assumptions, I demonstrate that a certain district magnitude maximizes the expected seat share of a particular median-sized party in elections using the d'Hondt PR or SNTV formulae. The validity of this threshold model is verified by an empirical study on recent elections in Finland & Taiwan. 2 Tables, 2 Figures, 1 Appendix, 19 References. Adapted from the source document.