Voting theory

The electoral system of a country or institution includes the all the rules and processes it has surrounding elections and referendums. Such rules determine when and on what matters elections are held; who is eligible to vote in those elections; how votes are cast and what set of rules which must be followed for a vote to be considered valid; if and how multiple rounds of voting are used; and how votes are counted and aggregated to yield a final result. This last aspect, the algorithm for aggregating votes into a result, is called the "voting method" or "voting rule", and is central to an electoral system. Electoral systems are often characterized by the primary voting method they use; for instance, majority rule, proportional representation and plurality voting, aside from being voting methods, are considered to be types of electoral systems, as are variations such as first-past-the-post and preferential voting. The study of formally defined voting methods is called social choice theory or voting theory, a subfield of political science, economics, or mathematics.

Those who are unfamiliar with voting theory are often surprised to learn that electoral systems other than majority rule exist, or that disagreements exist over what it means to be supported by a majority. Depending on the meaning chosen, the common "majority rule" systems can produce results that the majority does not support. If every election had only two choices, the winner would be determined using majority rule alone. However, when there are more than two options, there may not be a single option that is most liked or most disliked by a majority. A simple choice does not allow voters to express the ordering or the intensity of their feeling. Different voting systems may give very different results, particularly in cases where there is no clear majority preference.

An electoral system specifies the form of the ballot, the set of allowable votes; and the tallying method, an algorithm for determining the outcome. This outcome may be a single winner, as in the case of a presidential election, or may result in multiple winners, such as in the election of a legislative body. The electoral system may also specify how voting power is distributed among the voters, and how voters are divided into subgroups (constituencies) whose votes are counted independently.

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