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Instant-runoff voting (IRV), also known as the alternative vote (AV), transferable vote, ranked choice voting, or preferential voting is an electoral system used to elect a single winner from a field of more than two candidates. It is a preferential voting system in which voters rank the candidates in order of preference rather than voting for a single candidate. Ballots are initially distributed based on each elector's first preference. If a candidate secures more than half of votes cast, that candidate wins. Otherwise, the candidate with the fewest votes is eliminated. Ballots assigned to the eliminated candidate are recounted and added to the totals of the remaining candidates based on who is ranked next on each ballot. This process continues until one candidate wins by obtaining more than half the votes. IRV has the effect of avoiding split votes when multiple candidates earn support from like-minded voters. For example, suppose there are two similar candidates A & B, and a third opposing candidate C, with raw popularity of 35%, 25% and 40% respectively. In a plurality voting system, candidate C may win with 40% of the votes, even though 60% of electors prefer either A or B. Alternatively, voters are pressured to choose the seemingly stronger candidate of either A or B, despite personal preference for the other, in order to help ensure the defeat of C. It is often the resulting situation that candidate A or B would never get to ballot, whereas voters would be presented a two candidate choice. With IRV, the electors backing B as their first choice can allocate their preferences as #1 for B and #2 for A, which means A will win despite the split vote in first choices. Instant-runoff voting is used in national elections in many different places: for example, it is used to elect members of the Australian House of Representatives and most Australian State Governments, the President of India, members of legislative councils in India, the President of Ireland, and the parliament in Papua New Guinea. The system is also used in local elections around the world, as well as by some political parties (to elect internal leaders) and private associations. IRV is described in ''Robert's Rules of Order Newly Revised'' (under the name "preferential voting"). ==Terminology== Instant-runoff voting derives its name from how ballot-count simulates a series of two-round system runoffs except that voter preference do not change between rounds.〔〕 Britons and Canadians〔(【引用サイトリンク】title=The Alternative Vote: No Solution to the Democratic Deficit )〕 generally call IRV the "Alternative Vote" (AV). Australians, who use IRV for most single winner elections call IRV "preferential voting," as does Robert's Rules of Order. Americans in San Francisco, California, Portland, Maine and Minneapolis, Minnesota call IRV "ranked choice voting". IRV occasionally is referred to as Ware's method after its inventor, American William Robert Ware. North Carolina law uses "instant runoff" to describe the contingent vote or "batch elimination" form of IRV in one-seat elections. A single second round of counting produces the top two candidates for a runoff election. 〔(【引用サイトリンク】title=S.L. 2006-192 )〕 Election officials in Hendersonville, North Carolina use "instant runoff" to describe a multi-seat election system that simulates in a single round of voting their previous system of multi-seat runoffs.〔(【引用サイトリンク】title=CITIZEN-TIMES: Capital Letters – Post details: No instant runoff in Hendersonville )〕 State law in South Carolina〔(【引用サイトリンク】title=South Carolina General Assembly : 116th Session, 2005-2006 )〕 and Arkansas use "instant runoff" to describe the practice of having certain categories of absentee voters cast ranked choice ballots before the first round of a runoff and counting those ballots in any subsequent runoff elections. When the single transferable vote (STV) system is applied to a single-winner election it becomes IRV. Some Irish observers mistakenly call IRV "proportional representation" based on the fact that the same ballot form is used to elect its president by IRV and parliamentary seats by STV, but IRV is a winner-take-all election method. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Instant-runoff voting」の詳細全文を読む スポンサード リンク
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