electoral system

Any set of rules whereby the votes of citizens determine the selection of executives and/or legislators. Electoral systems may be categorized in several ways. The most useful is probably a three-way division into plurality, majoritarian, and proportional systems. For national elections, plurality systems are found only in Great Britain and some former British colonies (including the United States and India) (see first-past-the-post). Majoritarian systems are found in France and Australia for legislative elections, and in about half of the countries with directly elected chief executives (see second ballot). There are many proportional systems in the democratic world; they differ widely and there is no agreed criterion whereby one may be judged better than another.

Each family of systems has a number of distinctive features. Plurality systems tend to concentrate the vote on the two leading parties (see Duverger's law) except where there are concentrated regional parties. Majoritarian systems are appropriate for presidential elections, since there is only one president who ought to have majority support at least against the last rival left in the field; therefore systems such as alternative vote are justifiable, though imperfect. However, using a majoritarian system to elect a legislature can lead to severe distortions. The number of parties elected under a proportional system is a function partly of the size of districts it employs (the more seats there are in each district, the more parties will tend to be represented), and partly of the underlying cleavages in the society.

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