A voting system is a means of choosing between a number of options, based on the input of a number of voters. Voting is perhaps best known for its use in elections, where political candidates are selected for public office. Voting can also be used to award prizes, to select between different plans of action, or by a computer program to determine a solution to a complex problem. Voting can be contrasted with consensus decision making.
A voting system consists of the rules for how voters express their desires, and how these desires are aggregated to yield a final result. The study of formally defined voting systems is called voting theory, a subfield of political science, economics or mathematics. Voting theory began in the 18th century and has led to several proposals for voting systems.
Most voting systems are based on the concept of majority rule, or the principle that more than half of the voters should get the outcome they want. Given the simplicity of majority rule, those who are unfamiliar with voting theory are often surprised that such a variety of voting systems exists, or that popular voting systems can produce results not supported by more than half the voters. If every election had only two choices, the winner would be determined using majority rule alone. However, when there are three or more options, there may not be a single option that is preferred by a majority. Different voting systems may give very different results, particularly in cases where there is no clear majority preference. Thus, the choice of voting system(s) is one important component of a democratic government.