Instant-runoff voting

Instant-runoff voting (IRV) is a ranked-choice voting system that works by last-candidate elimination. In the United Kingdom, it is generally called the alternative vote (AV). In the United States and Australia, IRV is sometimes referred to simply as ranked-choice voting (RCV) or preferential voting, but such terms are regarded as misnomers because of the wide variety of ranked-choice (preferential) voting systems other than IRV.

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Single-winner/majoritarian Plurality First-past-the-post Plurality at-large (plurality block voting) General ticket (party block voting) Multi-round voting Two-round Exhaustive ballot Primary election Nonpartisan unified top-four Majority at-large (two-round block voting) Ranked / preferential systems Instant-runoff (alternative vote) Contingent vote Coombs' method Condorcet methods (Copeland's, Dodgson's, Kemeny–Young, Minimax, Nanson's, ranked pairs, Schulze, Alternative Smith) Positional voting (Borda count, Nauru/Dowdall method) Bucklin voting Oklahoma primary electoral system Preferential block voting Cardinal / graded systems Score voting Approval voting Combined approval voting Unified primary Usual judgment Satisfaction approval voting Majority judgment STAR voting
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IRV elections are a virtual (instant) variant of multiple-round voting. In each round, voters choose a favourite candidate; the last-place finisher is eliminated and another round is held. IRV elections automate this process by having voters rank candidates from first to last in order of preference. All rounds can then be held instantly by reassigning each voter's ballot to their alternate (i.e. their second choice). This process continues until every candidate except one has been eliminated, at which point they are declared the winner.

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 used in city elections, the mayor is often elected through IRV. It is also used in choosing the Academy Award for Best Picture, and a non-instant variant is used for the TV show American Idol.

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