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Majority Loser Criterion
The majority loser criterion is a criterion to evaluate single-winner voting systems. The criterion states that if a majority of voters prefers every other candidate over a given candidate, then that candidate must not win. Either of the Condorcet loser criterion or the mutual majority criterion implies the majority loser criterion. However, the Condorcet criterion does not imply the majority loser criterion, since the minimax method satisfies the Condorcet but not the majority loser criterion. Also, the majority criterion is logically independent from the majority loser criterion, since the plurality rule satisfies the majority but not the majority loser criterion, and the anti-plurality rule satisfies the majority loser but not the majority criterion. There is no positional scoring rule which satisfies both the majority and the majority loser criterion, but several non-positional rules, including many Condorcet rules, do satisfy both criteria. Methods that comply with this ...
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Single-winner Voting System
A single-member district is an electoral district represented by a single officeholder. It contrasts with a multi-member district, which is represented by multiple officeholders. Single-member districts are also sometimes called single-winner voting, winner-takes-all, or single-member constituencies. A number of electoral systems use single-member districts, including plurality voting (first-past-the-post), two-round systems, instant-runoff voting (IRV), approval voting, range voting, Borda count, and Condorcet methods (such as the Minimax Condorcet, Schulze method, and Ranked Pairs). Of these, plurality and runoff voting are the most common. In some countries, such as Australia and India, members of the lower house of parliament are elected from single-member districts; and members of the upper house are elected from multi-member districts. In some other countries like Singapore, members of parliament can be elected from both single-member districts as well as multi-member dis ...
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Coombs' Method
Coombs' method or the Coombs ruleGrofman, Bernard, and Scott L. Feld (2004"If you like the alternative vote (a.k.a. the instant runoff), then you ought to know about the Coombs rule,"''Electoral Studies'' 23:641-59. is a ranked voting system which uses a ballot counting method for ranked voting created by Clyde Coombs. The Coombs' method is the application of Coombs rule to single-winner elections, similarly to instant-runoff voting, it uses candidate elimination and redistribution of votes cast for that candidate until one candidate has a majority of votes. Procedures Each voter rank-orders all of the candidates on their ballot. If at any time one candidate is ranked first (among non-eliminated candidates) by an absolute majority of the voters, that candidate wins. Otherwise, the candidate ranked last (again among non-eliminated candidates) by the largest number of (or a plurality of) voters is eliminated. Conversely, under instant-runoff voting, the candidate ranked first (amon ...
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Mutual Majority Criterion
The mutual majority criterion is a criterion used to compare voting systems. It is also known as the majority criterion for solid coalitions and the generalized majority criterion. The criterion states that if there is a subset S of the candidates, such that more than half of the voters strictly prefer every member of S to every candidate outside of S, this majority voting sincerely, the winner must come from S. This is similar to but stricter than the majority criterion, where the requirement applies only to the case that ''S'' contains a single candidate. This is also stricter than the majority loser criterion, where the requirement applies only to the case that ''S'' contains all but one candidate. The mutual majority criterion is the single-winner case of the Droop proportionality criterion. The Schulze method, ranked pairs, instant-runoff voting, Nanson's method, and Bucklin voting pass this criterion. All Smith-efficient Condorcet methods pass the mutual majority criterion ...
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Majority Criterion
The majority criterion is a single-winner voting system criterion, used to compare such systems. The criterion states that "if one candidate is ranked first by a majority (more than 50%) of voters, then that candidate must win". Some methods that comply with this criterion include any Condorcet method, Instant-runoff voting, Bucklin voting, and Plurality voting. The criterion was originally defined in relation to methods which rely only on ranked ballots (voted preference orders of the candidates), so while ranked methods such as the Borda count fail the criterion under any definition, its application to methods which give weight to preference strength is disputed. For these methods, such as STAR voting, Score (Range) voting, Approval voting and Majority Judgment, the system may pass or fail depending on the definition of the criterion which is used. Advocates of other voting systems contend that the majority criterion is actually a ''flaw'' of a voting system, and not a featur ...
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Score Voting
Score voting or range voting is an electoral system for single-seat elections, in which voters give each candidate a score, the scores are added (or averaged), and the candidate with the highest total is elected. It has been described by various other names including evaluative voting, utilitarian voting, interval measure voting, the point system, ratings summation, 0-99 voting, average voting and utility voting. It is a type of cardinal voting electoral system, and aims to implement the utilitarian social choice rule. Score voting should be distinguished from positional voting systems, such as the Borda count: in score voting, each voter is free to give any score to any candidate; in positional voting, the score that each voter gives to each candidate is uniquely determined by the candidate's rank in the voter's ballot. Usage Political use Combined approval voting, a 3-rank form of score voting, is used to determine which candidates represent the parties in Latvia's Saei ...
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Approval Voting
Approval voting is an electoral system in which voters can select many candidates instead of selecting only one candidate. Description Approval voting ballots show a list of the options of candidates running. Approval voting lets each voter indicate support for one or more candidates. Final tallies show how many votes each candidate received, and the winner is the candidate with the most support. Effect on elections Approval voting advocates Steven Brams and Dudley R. Herschbach predict that approval voting should increase voter participation, prevent minor-party candidates from being spoilers, and reduce negative campaigning. FairVote published a position paper arguing that approval voting has three flaws that undercut it as a method of voting and political vehicle (the group instead advocates for Instant-runoff voting). They argue that it can result in the defeat of a candidate who would win an absolute majority in a plurality election, can allow a candidate to win who ...
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Contingent Vote
The contingent vote is an electoral system used to elect a single representative in which a candidate requires a majority of votes to win. It is a variation of instant-runoff voting (IRV). Under the contingent vote, the voter ranks the candidates in order of preference, and the first preference votes are counted. If no candidate has a majority (more than half the votes cast), then all but the two leading candidates are eliminated and the votes received by the eliminated candidates are distributed among the two remaining candidates according to voters' preferences. This ensures that one candidate achieves a majority and is declared elected. The contingent vote differs from IRV which allows for many rounds of counting, eliminating only one weakest candidate each round. IRV allows a small chance the candidate outside the top two can still win. The contingent vote can also be considered a compressed form of the two-round system (runoff system), in which both 'rounds' occur witho ...
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Plurality Voting System
Plurality voting refers to electoral systems in which a candidate, or candidates, who poll more than any other counterpart (that is, receive a plurality), are elected. In systems based on single-member districts, it elects just one member per district and may also be referred to as first-past-the-post (FPTP), single-member plurality (SMP/SMDP), single-choice voting (an imprecise term as non-plurality voting systems may also use a single choice), simple plurality or relative majority (as opposed to an ''absolute majorit''y, where more than half of votes is needed, this is called ''majority voting''). A system which elects multiple winners elected at once with the plurality rule, such as one based on multi-seat districts, is referred to as plurality block voting. Plurality voting is distinguished from ''majority voting'', in which a winning candidate must receive an absolute majority of votes: more than half of all votes (more than all other candidates combined if each voter ha ...
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Anti-plurality Voting
Anti-plurality voting describes an electoral system in which each voter votes ''against'' a single candidate, and the candidate with the fewest votes against wins. Anti-plurality voting is an example of a positional voting method. Example In this electoral system, each voter marks a vote against his or her fourth preference. In this case, it would be a tie between Nashville and Chattanooga, both receiving zero votes. If the tie is to be resolved with anti-plurality voting as well, Nashville would win, as it has less second-to-last place votes (32%) than Chattanooga (42%). Ties could also be resolved through a second subsequent runoff election. Characteristics As can be seen from the example, in the absence of tactical voting, this system tends to favor middle-of-the-road candidates. However, it is very sensitive to tactical voting, as any candidate perceived beforehand as a potential winner will attract more countervotes from partisans of their opponents. This creates the p ...
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Contingent Vote
The contingent vote is an electoral system used to elect a single representative in which a candidate requires a majority of votes to win. It is a variation of instant-runoff voting (IRV). Under the contingent vote, the voter ranks the candidates in order of preference, and the first preference votes are counted. If no candidate has a majority (more than half the votes cast), then all but the two leading candidates are eliminated and the votes received by the eliminated candidates are distributed among the two remaining candidates according to voters' preferences. This ensures that one candidate achieves a majority and is declared elected. The contingent vote differs from IRV which allows for many rounds of counting, eliminating only one weakest candidate each round. IRV allows a small chance the candidate outside the top two can still win. The contingent vote can also be considered a compressed form of the two-round system (runoff system), in which both 'rounds' occur witho ...
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Instant-runoff Voting
Instant-runoff voting (IRV) is a type of ranked preferential voting method. It uses a majority voting rule in single-winner elections where there are more than two candidates. It is commonly referred to as ranked-choice voting (RCV) in the United States (although there are other forms of ranked voting), 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 means only its multi-winner variant. All these names are often used inconsistently. Voters in IRV elections rank the candidates in order of preference. Ballots are initially counted for each voter's top choice. 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 the defeated candidate as a first choice then have their vot ...
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Bucklin Voting
Bucklin voting is a class of voting methods that can be used for single-member and multi-member districts. As in highest median rules like the majority judgment, the Bucklin winner will be one of the candidates with the highest median ranking or rating. It is named after its original promoter, the Georgist politician James W. Bucklin of Grand Junction, Colorado, and is also known as the Grand Junction system. Voting process Bucklin rules varied, but here is a typical example: Voters are allowed rank preference ballots (first, second, third, etc.). First choice votes are first counted. If one candidate has a majority, that candidate wins. Otherwise the second choices are added to the first choices. Again, if a candidate with a majority vote is found, the winner is the candidate with the most votes accumulated. Lower rankings are added as needed. A majority is determined based on the number of valid ballots. Since, after the first round, there may be more votes cast than vo ...
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