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In Australian politics the two-party-preferred vote (TPP or 2PP) is the result of an election or opinion poll after preferences have been distributed to the last two parties. For the purposes of TPP, the Liberal/National Coalition is usually considered a single party, with Labor being the other major party. Typically the TPP is expressed as the percentages of votes attracted by each of the two major parties, e.g. "Coalition 45%, Labor 55%", where the values include both primary votes and preferences. The TPP is an indicator of how much swing has been attained/is required to change the result, taking into consideration preferences, which may have a significant effect on the result. The TPP assumes a two-party system, i.e. that after distribution of votes from less successful candidates, the two remaining candidates will be from the two major parties. However, in some electorates this is not the case. The two-candidate-preferred vote (TCP) is the result after preferences have been distributed, using instant-runoff voting, to the final two candidates, regardless of which party the candidates represent. For electorates where these two candidates are from the major parties, the TCP is also the TPP. For electorates where these two candidates are not both from the major parties, preferences are notionally distributed to the two major parties to determine the TPP. In this case the TPP differs from the TCP, and is informative but has no effect on the election outcome. TPP results above seat-level, such as a national or statewide TPP, are also informative only and has no result on the election outcome. The full allocation of preferences under instant-runoff voting is used in the lower houses of the Federal, Victorian, Western Australian, South Australian, and Northern Territory parliaments, as well as the upper house of Tasmania. The New South Wales lower house and Queensland use optional-preference instant runoff voting – with some votes giving limited or no preferences, TPP/TCP is not as meaningful. TPP/TCP does not occur in the Tasmanian lower house or the Australian Capital Territory due to a different system altogether, the Hare-Clark proportional voting system. Aside from Tasmania, TPP/TCP is not used in any other upper houses in Australia, with most using the group ticket single transferable proportional voting system.〔(【引用サイトリンク】title=How the House of Representatives votes are counted )〕 ==History== Australia originally used first-past-the-post voting as used by the House of Commons of the United Kingdom. Federal election full-preference instant-runoff voting has been in existence since its introduction by the government after the 1918 Swan by-election. Candidates from the Australian Labor Party, the Nationalist Party government (predecessor to the United Australia Party and Liberal Party of Australia), and the emerging National Party of Australia (then Country Party) all received around a third of the vote, however Labor remained a few percent in front of both other candidates to win the seat. The system has allowed the two non-Labor parties to compete in many seats without splitting the conservative vote in three-cornered-contests. Even in landslide conservative election wins such as 1975 or 1996, Labor had the largest primary vote. The Coalition now comprises four parties: the Liberal Party of Australia except Queensland and the Northern Territory, the National Party of Australia in New South Wales and Victoria, the Liberal National Party of Queensland, and the Country Liberal Party in the Northern Territory. It is increasingly uncommon for seats to be contested by more than one Coalition candidate, by 2010 only three seats were contested by more than one Coalition candidate, all in New South Wales. Four seats were contested by the non-Coalition National Party of Western Australia, none were contested by the non-Coalition National Party of South Australia, and neither are automatically part of the Coalition TPP. Preferences have also been of significant relevance to the DLP, the Democrats, One Nation, the Greens, and independents. Not distributing preferences was historically common in seats where a candidate received over 50 percent of the primary vote. Federal seat and national TPP results have only been produced as far back as 1937, though it was not uncommon in the next few decades for major parties at federal elections to not field a candidate in a few "safe" seats, but since 1972, all seats at federal elections have been contested by the major parties. Full preference distributions have occurred in all seats since 1983.〔(Historical national and state-by-state two-party preferred results: Australian Electoral Commission )〕 South Australian state elections have boundaries strategically redrawn before each election with a fairness aim based on the prior election TPP vote, the only state to do so. The culmination of the historical state lower house seat malapportionment known as the Playmander eventually saw it legislated after 1989 that the Electoral Commission of South Australia redraw boundaries after each election with the objective of the party that receives over 50 percent of the TPP vote at each forthcoming election forms government. Nationally in 1983/84, minor gerrymandering by incumbent federal governments was legislated against with the formation of the independent Commonwealth statutory authority, the Australian Electoral Commission.〔(The Results and the Pendulum – Malcolm Mackerras: Australian National University )〕 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「Two-party-preferred vote」の詳細全文を読む スポンサード リンク
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