Voting information project

The preferred turnout rates are those calculated with the voting-eligible population as the denominator. The voting-eligible population VEP represents an estimate of persons eligible to vote regardless of voter registration status in an election and is constructed by modifying the voting-age population VAPby components reported in the right-most columns scroll right in the spreadsheet.

Voting information project

No ranked-preference method can meet all of the criteria, because some of them are mutually exclusive, as shown by statements such as Arrow's impossibility theorem and the Gibbard—Satterthwaite theorem. Many of the mathematical criteria by which voting methods are compared were formulated for voters with ordinal preferences.

If voters vote according to the same ordinal preferences in both rounds, criteria can be applied to two-round systems of runoffs, and in that case, each of the criteria failed by IRV is also failed by the two-round system as they relate to automatic elimination of trailing candidates.

Partial results exist for other models of voter behavior in the two-round method: Satisfied Criteria[ edit ] Condorcet loser criterion The Condorcet loser criterion states that "if a candidate would lose a head-to-head competition against every other candidate, then that candidate must not win the overall election".

Independence of clones criterion The independence of clones criterion states that "the election outcome remains the same even if an identical candidate who is equally preferred decides to run.

Majority criterion The majority criterion states that "if one candidate is preferred by an absolute majority of voters, then that candidate must win". Mutual majority criterion The mutual majority criterion states that "if an absolute majority of voters prefer every member of a group of candidates to every candidate not in that group, then one of the preferred group must win".

Resolvability criterion The resolvability criterion states that "the probability of an exact tie must diminish as more votes are cast". Non-satisfied Criteria[ edit ] Condorcet winner criterion The Condorcet winner criterion states that "if a candidate would win a head-to-head competition against every other candidate, then that candidate must win the overall election".

It is incompatible with the later-no-harm criterion, so IRV does not meet this criterion. IRV is more likely to elect the Condorcet winner than plurality voting and traditional runoff elections. The California cities of Oakland, San Francisco and San Leandro in provide an example; there were a total of four elections in which the plurality-voting leader in first-choice rankings was defeated, and in each case the IRV winner was the Condorcet winner, including a San Francisco election in which the IRV winner was in third place in first choice rankings.

IRV, like all preferential voting methods which are not positionaldoes not meet this criterion. Independence of irrelevant alternatives criterion The independence of irrelevant alternatives criterion states that "the election outcome remains the same even if a candidate who cannot win decides to run.


Some critics [44] argue in turn that Allard's calculations are wrong and the probability of monotonicity failure is much greater, at IRV does not meet this criterion: For example, the elimination of the candidate with the most last-place rankings, rather than the one with the fewest first-place rankings, is called Coombs' methodand universal assignment of numerical values to each rank is used in the Borda count method.

A chart in the article on the Schulze method compares various ranked ballot methods. Comparison to first-past-the-post[ edit ] At the Australian federal election in Septemberout of the House of Representatives seats or 90 percent were won by the candidate who led on first preferences.

The other 15 seats 10 percent were won by the candidate who placed second on first preferences. This implies that IRV is susceptible to tactical voting in some circumstances.

Research concludes that IRV is one of the less-manipulable voting methods, with theorist Nicolaus Tideman noting that, "alternative vote is quite resistant to strategy" [50] and Australian political analyst Antony Green dismissing suggestions of tactical voting.

The change in lower candidates is important: Tactical voting in IRV seeks to alter the order of eliminations in early rounds, to ensure that the original winner is challenged by a stronger opponent in the final round. For example, in a three-party election where voters for both the left and right prefer the centrist candidate to stop the "enemy" candidate winning, those voters who care more about defeating the "enemy" than electing their own candidate may cast a tactical first preference vote for the centrist candidate.

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The mayoral election in Burlington, Vermont provides an example in which strategy theoretically could have worked but would have been unlikely in practice.

In that election, most supporters of the candidate who came in second a Republican who led in first choices preferred the Condorcet winner, a Democrat, to the IRV winner, the Progressive Party nominee.

Voting information project

Yet because the Republican led in first choices and only narrowly lost the final instant runoff, his backers would have been highly unlikely to pursue such a strategy. Spoiler effect The spoiler effect is when a difference is made to the anticipated outcome of an election due to the presence on the ballot paper of a candidate who predictably will lose.

Most often this is when two or more politically similar candidates divide the vote for the more popular end of the political spectrum. That is, each receives fewer votes than a single opponent on the unpopular end of the spectrum who is disliked by the majority of voters but who wins from the advantage that, on that unpopular side, he or she is unopposed.

Under a plurality method, voters who sympathize most strongly with a marginal candidate are strongly encouraged to instead vote for a more popular candidate who shares some of the same principles, since that candidate has a much greater chance of being elected and a vote for the marginal candidate will not result the marginal candidate's election.

An IRV method reduces this problem, since the voter can rank the marginal candidate first and the mainstream candidate second; in the likely event that the fringe candidate is eliminated, the vote is not wasted but is transferred to the second preference.

However, when the third party candidate is more competitive, they can still act as a spoiler under IRV, [60] [61] [62] [63] [64] [65] by taking away first-choice votes from the more mainstream candidate until that candidate is eliminated, and then that candidate's second-choice votes helping a more-disliked candidate to win.

In these scenarios, it would have been better for the third party voters if their candidate had not run at all spoiler effector if they had voted dishonestly, ranking their favorite second rather than first favorite betrayal.

In that sense, the Republican candidate was a spoiler even though leading in first choice support. Other Condorcet methods also elect from these sets using different rules; Tideman's is the most functionally-similar to IRV.Brazil (voting machines) The beginning of the Brazilian e-voting endeavour can be dated back to , when a computerized election database was being implemented by the Superior Electoral Court.

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Thank you for printing our content at Please check back to find out the latest information regarding absentee voting. A number of different turnout rates are presented here. The preferred turnout rates are those calculated with the voting-eligible population as the denominator.

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