Electoral Systems

Abstract

An electoral system is a set of rules governing an election, and many scholars distinguish between three main elements of any system: ballot structure (how and ‘for what’ a vote is cast); constituency structure (whether, and how, the electorate is divided into territorially defined constitutencies), and the electoral formula (in an assembly election this is the method of translating votes into seats). The main types of electoral formulae are majoritarian, plurality, and proportional. The most common way of classifying electoral systems is to distinguish between proportional (PR) and nonproportional systems. The two main variants of the former are party-list systems and the single transferable vote (STV); the three main variants of the latter are plurality, majoritarian, and (so-called) semiproportional systems. Much debate has focused on the effects of electoral systems, and on ‘Duverger's law.’ However, most political scientists now argue that the electoral system has only a limited effect on a regime's party system, and hence on its potential for instability. However, the timing of the adoption of PR systems does have an effect, with its early introduction increasing the likelihood of fragmentation in the party system. Moreover, at particular junctures, changes in the electoral system can affect which parties are likely to govern a regime.