Manuscript Who gains from apparentments under D’Hondt? Daniel Bochsler, Centre for the Study of Imperfections in Democracies (DISC), Central European University,
[email protected] - www.bochsler.eu 13 November 2009 Apparentments – or coalitions of several electoral lists – are a widely neglected aspect of the study of proportional electoral systems. This paper proposes a formal model that explains the benefits political parties derive from apparentments, based on their alliance strategies and relative size. In doing so, it reveals that apparentments are most beneficial for highly fractionalised political blocs. However, it also emerges that large parties stand to gain much more from apparentments than small parties do. Because of this, small parties are likely to join in apparentments with other small parties, excluding large parties where possible. These arguments are tested empirically, using a new dataset from the Swiss national parliamentary elections covering a period from 1995 to 2007. Keywords: Electoral systems; apparentments; mechanical effect; PR; D’Hondt. Apparentments, a neglected feature of electoral systems* Seat allocation rules in proportional representation (PR) systems have been subject to widespread political debate, and one particularly under-analysed subject in this area is list apparentments. Theoretical work and studies based on simulation models has shown that the division allocation rule with rounding down (the most frequently applied PR allocation rule, referred to as the D’Hondt or Jefferson method) strongly favours large parties over small parties (see, among many others, Pennisi, 1998; Elklit, 2007; Schuster, Pukelsheim, Drton, and Draper, 2003). Other common seat allocation rules, such as Hamilton’s or Hare/Niemayer’s largest remainder method, or the Sainte- Laguë/Webster divisor method with standard rounding are unbiased with regards to party size.