Instant-runoff voting

Instant-runoff voting (IRV) is an electoral system that uses ranked voting. Its purpose is to elect the majority choice in single-member districts in which there are more than two candidates and thus help ensure majority rule. It is a single-winner version of single transferable voting. Formerly the term "instant-runoff voting" was used for what many people now call contingent voting or supplementary vote. In the United States, IRV is commonly referred to as ranked-choice voting (RCV) (although there are other forms of ranked voting), and it is called preferential voting in Australia, where it has seen the widest adoption. In the United Kingdom, it is generally called alternative vote (AV), whereas in some other countries it is referred to as the single transferable vote, which usually refers to only its multi-winner variant. These names are often used inconsistently. Voters in IRV elections rank the candidates in order of preference. Ballots are initially counted to establish the number of votes for each candidate. If a candidate has more than half of the first-choice votes, that candidate wins. If not, then the candidate with the fewest votes is eliminated, and the voters who selected that candidate as their first choice have their votes added to the total of the candidate who was their next choice. That process continues until one candidate has more than half of the votes, and that person is declared the winner. IRV is not a proportional voting system but a "winner-takes-all" method, because it results in only one winner in one district. IRV is used in national elections in several countries. In Australia, it is used to elect members of the federal House of Representatives, as well as the lower houses in most states, and in some local government elections. It is the method used to elect the President of India, the President of Ireland, and (in a modified form) the National Parliament of Papua New Guinea. When STV is used in city elections, the mayor is often elected through IRV.