Electoral systems and unimagined consequences: Partisan effects of districted proportional representation

Electoral systems scholarship has frequently focused on the role of district magnitude - the number of seats awarded per district - in shaping party systems. The basic insight is that an increase in district magnitude will tend to increase the number of parties and party system fragmentation. District magnitude varies in many electoral systems, but cross-national research summarizes this distribution with a single number. We argue here that magnitude variation itself has important partisan political consequences, which we refer to collectively as the "variance effect." The variance effect creates disadvantages for urban political interests relative to rural interests, making it more difficult for urban and other correlated interests to convert support into parliamentary representation and to obtain unfragmented parliamentary representation. We demonstrate, with analyses of twenty-four elections in sixteen countries, that the variance effect operates as theoretically predicted and is surprisingly important.