Instant-runoff voting

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Instant-runoff voting (IRV), also known as plurality with elimination or plurality loser,^[1] is a ranked-choice voting system that modifies plurality by repeatedly eliminating the last-place winner until only one candidate is left.^[2][3] In the United Kingdom, it is generally called the alternative vote (AV).^[4] In the United States, IRV is often referred to as ranked-choice voting (RCV), by way of conflation with ranked voting systems in general.^[5]

IRV elections are a virtual (instant) variant on exhaustive elimination. 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. Voting can then be completed "instantly" by automatically reassigning each voter's ballot to their alternate (i.e. second) choice. This process continues until every candidate except one has been eliminated, at which point they are declared the winner. A similar procedure is used in instant round-robin voting, which automatically compares pairs of candidates to find a tournament winner.

IRV is used in national elections in several countries. In Australia, it is used to elect members of the federal House of Representatives,^[6] as well as the lower houses in most states, and in some local government elections. It is used to elect the president of India, the president of Ireland,^[7] the National Parliament of Papua New Guinea,^[8] and the Academy Award for Best Picture.^[9]