Instant-runoff voting (IRV) is a type of ranked preferential voting method used in single-seat elections with more than two candidates. Instead of indicating support for only one candidate, voters in IRV elections can 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 vote based on first-choices, that candidate wins. If not, then the candidate with the fewest votes is eliminated. The voters who selected the defeated candidate as a first choice then have their votes added to the totals of their next choice. This process continues until a candidate has more than half of the votes. When the field is reduced to two, it has become an "instant runoff" that allows a comparison of the top two candidates head-to-head.
Instant-runoff voting is used in national elections in several countries. For example, it is used to elect members of the Australian House of Representatives and most Australian state legislatures; the President of India and members of legislative councils in India; the President of Ireland; adopted and being used to elect members of Congress in Maine in the United States; and the parliament in Papua New Guinea. The method is also used in local elections around the world, as well as by some political parties (to elect internal leaders) and private associations, for various voting purposes such as that for choosing the Academy Award for Best Picture. IRV is described in Robert's Rules of Order Newly Revised as an example of preferential voting.
It is also sometimes referred to as the alternative vote or ranked-choice voting. IRV can also be considered to be a variant of the single transferable vote system.
Instant-runoff voting derives its name from the way the ballot count simulates a series of runoffs, similar to a two-round system, except that voter preferences do not change between rounds. It is also known as the alternative vote, transferable vote, ranked-choice voting (RCV), single-seat ranked-choice voting, or preferential voting. Britons generally call IRV the "Alternative Vote" (AV) while in Canada it is called "Ranked Choice" or "Ranked Choice Voting". Australians, who use IRV for most single winner elections, call IRV "preferential voting", as does Robert's Rules of Order. IRV occasionally is referred to as Ware's method after its inventor, American William Robert Ware. American organizations that promote IRV (such as FairVote) identified IRV as "instant-runoff voting" as recently as 2009, but shifted to referring to IRV as "ranked-choice voting" as jurisdictions using it such as San Francisco, California; Maine; and Minneapolis, Minnesota codified the term in their laws.
When the single transferable vote (STV) method 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.
North Carolina law used "instant runoff" to describe the contingent vote or "batch elimination" form of IRV in one-seat elections prior to IRV being eliminated in 2013. A single second round of counting produces the top two candidates for a runoff election. Election officials in Hendersonville, North Carolina used "instant runoff" to describe a multi-seat election method that simulates in a single round of voting their previous method of multi-seat runoffs. State law in South Carolina 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.
There are a number of variations in IRV. IRV methods in use in different countries vary, both as to ballot design and as to whether or not voters are obliged to provide a full list of preferences.
In an optional preferential voting system, voters can give a preference to as many candidates as they wish. They may make only a single choice, known as "bullet voting", and some jurisdictions accept an "X" as valid for the first preference. This may result in ballot exhaustion, where all the voters' preferences are eliminated before a candidate is elected with a majority. Optional preferential voting is used for elections for the President of Ireland and the Western Australian Legislative Assembly.
In a full preferential voting method, voters are required to mark a preference for every candidate standing. Ballots that do not contain a complete ordering of all candidates are in some jurisdictions considered spoilt or invalid, even if there are only two candidates standing. This can become burdensome in elections with many candidates and can lead to "donkey voting", in which some voters simply choose candidates at random or in top-to-bottom order, or a voter may order his or her preferred candidates and then fill in the remainder on a donkey basis. Full preferential voting is used for elections to the Australian federal parliament and for most State parliaments.
Other methods only allow marking preferences for a maximum of the voter's top three favorites, a form of partial preferential voting.
Instant-runoff voting was devised in 1871 by American architect William Robert Ware, although it is, in effect, a special case of the single transferable vote method, which emerged independently in the 1850s. Unlike the single transferable vote in multi-seat elections, however, the only ballot transfers are from backers of candidates who have been eliminated.
The first known use of an IRV-like method in a governmental election was in the 1893 general election in the Colony of Queensland (in present-day Australia). The variant used for this election was a "contingent vote". IRV in its true form was first used in Western Australia, in the 1908 state election. The Hare-Clark system was introduced for the Tasmanian House of Assembly at the 1909 state election.
IRV was introduced for federal (nationwide) elections in Australia after the Swan by-election in October 1918, in response to the rise of the conservative Country Party, representing small farmers. The Country Party split the non-Labor vote in conservative country areas, allowing Labor candidates to win without a majority of the vote. The conservative government of Billy Hughes introduced IRV (in Australia called "preferential voting") as a means of allowing competition between the Coalition parties without putting seats at risk. It was first used at the Corangamite by-election on 14 December 1918, and at a national level at the 1919 election. IRV continued to benefit the Coalition until the 1990 election, when for the first time Labor obtained a net benefit from IRV.
In instant-runoff voting, as with other ranked election methods, each voter ranks the list of candidates in order of preference. Under a common ballot layout, the voter marks a '1' beside the most preferred candidate, a '2' beside the second-most preferred, and so forth, in ascending order. This is shown in the example Australian ballot above.
The mechanics of the process are the same regardless of how many candidates the voter ranks, and how many are left unranked. In some implementations, the voter ranks as many or as few choices as they wish, while in other implementations the voter is required to rank either all candidates, or a prescribed number of them.
In the initial count, the first preference of each voter is counted and used to order the candidates. Each first preference counts as one vote for the appropriate candidate. Once all the first preferences are counted, if one candidate holds a majority, that candidate wins. Otherwise the candidate who holds the fewest first preferences is eliminated. If there is an exact tie for last place in numbers of votes, various tie-breaking rules determine which candidate to eliminate. Some jurisdictions eliminate all low-ranking candidates simultaneously whose combined number of votes is fewer than the number of votes received by the lowest remaining candidates.
Ballots assigned to eliminated candidates are added to the totals of one of the remaining candidates based on the next preference ranked on each ballot. The process repeats until one candidate achieves a majority of votes cast for continuing candidates. Ballots that 'exhaust' all their preferences (all its ranked candidates are eliminated) are set aside.
In Australian elections the allocation of preferences is performed efficiently in an unofficial tally at the polling booth by having the returning officer pre-declare the two most likely winners. (In the event that the returning officer is wrong the votes need to be recounted.)
The common way to list candidates on a ballot paper is alphabetically or by random lot. In some cases, candidates may also be grouped by political party. Alternatively, Robson Rotation involves randomly changing candidate order for each print run.
Where preferential voting is used for the election of an assembly or council, parties and candidates often advise their supporters on their lower preferences, especially in Australia where a voter must rank all candidates to cast a valid ballot. This can lead to "preference deals", a form of pre-election bargaining, in which smaller parties agree to direct their voters in return for support from the winning party on issues critical to the small party. However, this relies on the assumption that supporters of a minor party will mark preferences for another party based on the advice that they have been given.
Most IRV elections historically have been tallied by hand, including in elections to Australia's House of Representatives and most state governments. In the modern era, voting equipment can be used to administer the count either partially or fully.
In Australia, the returning officer now usually declares the two candidates that are most likely to win each seat. The votes are always counted by hand at the polling booth monitored by scrutineers from each candidate. The first part of the count is to record the first choice for all candidates. Votes for candidates other than the two likely winners are then allocated to them in a second pass. The whole process of counting the votes by hand and allocating preferences is typically completed within two hours on election night at a cost of $7.68 per elector in 2010 to run the entire election.
(The declaration by the returning officer is simply to optimize the counting process. In the unlikely event that the returning officer is wrong and a third candidate wins, then the votes would simply have to be counted a third time.)
Ireland in its presidential elections has several dozen counting centers around the nation. Each center reports its totals and receives instructions from the central office about which candidate or candidates to eliminate in the next round of counting based on which candidate is in last place. The count typically is completed the day after the election, as in 1997.
In the United States, some Californian cities, e.g. Oakland and San Francisco, administer IRV elections on voting machines, with optical scanning machines recording preferences and software tallying the IRV algorithm as soon as ballots are tallied. Cary, North Carolina's pilot program in 2007 tallied first choices on optical scan equipment at the polls and then used a central hand-count for the IRV tally. Portland, Maine in 2011 used its usual voting machines to tally first choice at the polls, then a central scan with different equipment if an IRV tally was necessary.
Some examples of IRV elections are given below. The first two (fictional elections) demonstrate the principle of IRV. The others offer examples of the results of real elections.
A simple example is provided in the accompanying table. Three candidates are running for election, Bob, Bill and Sue. There are five voters, "a" through "e". The voters each have one vote. They rank the candidates first, second and third in the order they prefer them. To win, a candidate must have a majority of vote; that is, three or more.
In Round 1, the first-choice rankings are tallied, with the results that Bob and Sue both have two votes and Bill has one. No candidate has a majority, so a second "instant runoff" round is required. Since Bill is in bottom place, he is eliminated. The ballot from any voter who ranked Bill first (in this example solely voter "c" ) gets modified as follows: the original 2nd choice candidate for that voter becomes their new 1st choice, and their original 3rd choice becomes their new 2nd choice. This results in the Round 2 votes as seen below. This gives Sue 3 votes, which is a majority.
|Round 1||Round 2|
Most instant-runoff voting elections are won by the candidate who leads in first-choice rankings. In such cases, IRV chooses the same winner as first-past-the-post voting. Some IRV elections are won by a candidate who finishes second after the first-round count. In this case, IRV chooses the same winner as a two-round system if all voters were to vote again and maintain their same preferences. A candidate may also win who is in third place or lower after the first count, but gains majority support in the final round. In such cases, IRV would choose the same winner as a multi-round method that eliminated the last-place candidate before each new vote, assuming all voters kept voting and maintained their same preferences. Here is an example of this last case.
Imagine that Tennessee is having an election on the location of its capital. The population of Tennessee is concentrated around its four major cities, which are spread throughout the state. For this example, suppose that the entire electorate lives in these four cities and that everyone wants to live as near to the capital as possible.
The candidates for the capital are:
The preferences of the voters would be divided like this:
|42% of voters
(close to Memphis)
|26% of voters
(close to Nashville)
|15% of voters
(close to Chattanooga)
|17% of voters|
(close to Knoxville)
It takes three rounds to determine a winner in this election.
Round 1 – In the first round no city gets a majority:
|Votes in round/
If one of the cities had achieved a majority vote (more than half), the election would end there. If this were a first-past-the-post election, Memphis would win because it received the most votes. But IRV does not allow a candidate to win on the first round without having an absolute majority of the vote. While 42% of the electorate voted for Memphis, 58% of the electorate voted against Memphis in this first round.
Round 2 – In the second round of tabulation, we remove the city with the least first-place support from consideration. Chattanooga received the lowest number of votes in the first round, so it is eliminated. The ballots that listed Chattanooga as first choice are added to the totals of the second-choice selection on each ballot. Everything else stays the same.
Chattanooga's 15% of the total votes are added to the second choices selected by the voters for whom that city was first-choice (in this example Knoxville):
|Votes in round/
In the first round, Memphis was first, Nashville was second and Knoxville was third. With Chattanooga eliminated and its votes redistributed, the second round finds Memphis still in first place, followed by Knoxville in second and Nashville has moved down to third place. This example however makes the unlikely assumption that all voters who selected a certain city first would rank the subsequent cities in the same order. In reality, some first-choice supporters of Chattanooga may have had Nashville as their second choice rather than Knoxville, resulting in Knoxville's elimination in Round 3.
Round 3 – No city yet has secured a majority of votes, so we move to the third round with the elimination of Nashville, and it becomes a contest between Memphis and Knoxville.
As in the second round with Chattanooga, all of the ballots currently counting for Nashville are added to the totals of Memphis or Knoxville based on which city is ranked next on that ballot. In this example the second-choice of the Nashville voters is Chattanooga, which is already eliminated. Therefore, the votes are added to their third-choice: Knoxville.
The third round of tabulation yields the following result:
|Votes in round/
Result: Knoxville, which was running third in the first tabulation, has moved up from behind to take first place in the third and final round. The winner of the election is Knoxville. However, if 6% of voters in Memphis were to put Nashville first, the winner would be Nashville, a preferable outcome for voters in Memphis. This is an example of potential tactical voting, though one that would be difficult for voters to carry out in practice. Also, if 17% of voters in Memphis were to stay away from voting, the winner would be Nashville. This is an example of IRV failing the participation criterion.
For comparison, note that traditional first-past-the-post voting would elect Memphis, even though most citizens consider it the worst choice, because 42% is larger than any other single city. As Nashville is a Condorcet winner, Condorcet methods would elect Nashville. A two-round method would have a runoff between Memphis and Nashville where Nashville would win, too.
|Candidates||1st Round||2nd Round||3rd Round|
Unlike Burlington's first IRV mayoral election in 2006, the IRV winner in 2009 (Bob Kiss) was neither the same as the plurality winner (Kurt Wright) nor the Condorcet winner (Andy Montroll). Because of the post-election controversy, IRV was repealed in 2010 by a vote of 52% to 48%.
The organization FairVote, which advocates for IRV, claimed the election as a success, citing three reasons (1) it prevented the election of the presumed winner under a plurality system by avoiding the effect of vote-splitting between the other candidates, (2) 99.99% of the ballots were valid suggesting that voters handled the system without difficulty, and (3) "contributed to producing a campaign among four serious candidates that was widely praised for its substantive nature." However, the election was considered a failure by advocates of the Condorcet winner, who point out that "in a head to head election, Andy Montroll should have beaten Bob Kiss by a 7.8% margin".
First Round VotesTransfer Votes
|Irish presidential election, 1990|
|Candidate||Round 1||Round 2|
The result of the 1990 Irish presidential election provides an example of how instant-runoff voting can produce a different result from first-past-the-post voting. The three candidates were Brian Lenihan of the traditionally dominant Fianna Fáil party, Austin Currie of Fine Gael, and Mary Robinson, nominated by the Labour Party and the Workers' Party. After the first round, Lenihan had the largest share of the first-choice rankings (and hence would have won a first-past-the-post vote), but no candidate attained the necessary majority. Currie was eliminated and his votes reassigned to the next choice ranked on each ballot; in this process, Robinson received 82% of Currie's votes, thereby overtaking Lenihan.
A good real-life example of IRV producing a result which differs from what would be expected of first-past-the-post or the two-round voting system is the result for the seat of Prahran at the 2014 Victorian state election. In this instance, the candidate who finished third (Greens candidate Sam Hibbins) in the primary vote would go on to win the seat on the back of favourable preferences from the other two minor parties and independents, narrowly beating the second-ranked candidate (Labor candidate Neil Pharaoh) by 31 votes and the first-ranked candidate (Liberal candidate Clem Newton-Brown) by 277 votes. It was not until the final round of counting that one of the two remaining candidates (Hibbins) had more than 50% of the total vote.
|Candidate||Primary Vote||First Round||Second Round||Third Round||Fourth Round||Fifth Round||Sixth Round|
|Clem Newton-Brown (LIB)||16,582||44.8%||16,592||16,644||16,726||16,843||17,076||18,363||49.6%|
|Neil Pharaoh (ALP)||9,586||25.9%||9,593||9,639||9,690||9,758||9,948|
|Sam Hibbins (GRN)||9,160||24.8%||9,171||9,218||9,310||9,403||9,979||18,640||50.4%|
|Eleonora Gullone (AJP)||837||2.3%||860||891||928||999|
|Alan Walker (FFP)||282||0.8%||283||295|
|Jason Goldsmith (IND)||247||0.7%||263||316||349|
|Steve Stefanopoulos (IND)||227||0.6%||241|
|Alan Menadue (IND)||82||0.2%|
Scholars rate voting methods using mathematically-derived voting method criteria, which describe desirable features of a method. 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: see the two-round system article's criterion compliance section for more information.
Condorcet loser criterion
Independence of clones criterion
Mutual majority criterion
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 2010 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.
The consistency criterion states that if dividing the electorate into two groups and running the same election separately with each group returns the same result for both groups, then the election over the whole electorate should return this result. IRV, like all preferential voting methods which are not positional, does 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." In the general case, instant-runoff voting can be susceptible to strategic nomination: whether or not a candidate decides to run at all can affect the result even if the new candidate cannot themselves win. This is much less likely to happen than under plurality.
The monotonicity criterion states that "a voter can't harm a candidate's chances of winning by voting that candidate higher, or help a candidate by voting that candidate lower, while keeping the relative order of all the other candidates equal." Allard claims failure is unlikely, at a less than 0.03% chance per election. Some critics argue in turn that Allard's calculations are wrong and the probability of monotonicity failure is much greater, at 14.5% under the impartial culture election model in the three-candidate case, or 7–10% in the case of a left-right spectrum. Lepelley et al. find a 2%–5% probability of monotonicity failure under the same election model as Allard.
The participation criterion states that "the best way to help a candidate win must not be to abstain". IRV does not meet this criterion: in some cases, the voter's preferred candidate can be best helped if the voter does not vote at all. Depankar Ray finds a 50% probability that, when IRV elects a different candidate than Plurality, some voters would have been better off not showing up.
Reversal symmetry criterion
The reversal symmetry criterion states that "if candidate A is the unique winner, and each voter's individual preferences are inverted, then A must not be elected". IRV does not meet this criterion: it is possible to construct an election where reversing the order of every ballot paper does not alter the final winner.
Instant-runoff voting is one of many ranked ballot methods. 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' method, and 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.
At the Australian federal election in September 2013, 135 out of the 150 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.
The Gibbard–Satterthwaite theorem demonstrates that no (deterministic, non-dictatorial) voting method using only the preference rankings of the voters can be entirely immune from tactical voting. 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" and Australian political analyst Antony Green dismissing suggestions of tactical voting. James Green-Armytage tested four ranked-choice methods, and found the alternative vote to be the second-most-resistant to tactical voting, though it was beaten by a class of AV-Condorcet hybrids, and did not resist strategic withdrawal by candidates well. Some simulations of several classes of voting methods in non-scholarly publications found IRV performed as badly as plurality when voters are strategic and fully informed about other voters' full preferences, and was out-performed by range voting, approval voting, and the Borda count.
By not meeting the monotonicity, Condorcet winner, and participation criteria, IRV permits forms of tactical voting when voters have sufficient information about other voters' preferences, such as from accurate pre-election polling. FairVote mentions that monotonicity failure can lead to situations where "Having more voters rank [a] candidate first, can cause [them] to switch from being a winner to being a loser." That assessment is accurate, although it only happens in particular situations. The change in lower candidates is important: whether votes are shifted to the leading candidate, shifted to a fringe candidate, or discarded altogether is of no importance.
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.
The 2009 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. If 371 (12.6%) out of the 2951 backers of the Republican candidate (those who also preferred the Democrat over the Progressive candidate for mayor) had insincerely raised the Democrat from their second choice to their first (not changing their rankings relative to their least favorite candidate, the Progressive), the Democrat would then have advanced to the final round (instead of their favorite), defeated any opponent, and proceeded to win the IRV election. This is an example of potential voter regret in that these voters who sincerely ranked their favorite candidate as first, find out after the fact that they caused the election of their least favorite candidate, which can lead to the voting tactic of compromising. 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.
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.
Proponents of IRV claim that IRV eliminates the spoiler effect, since IRV makes it safe to vote honestly for marginal parties: 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, 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 effect), or if they had voted dishonestly, ranking their favorite second rather than first (favorite betrayal).
For example, in the 2009 Burlington, Vermont mayoral election, if the Republican candidate who lost in the final instant runoff had not run, the Democratic candidate would have defeated the winning Progressive candidate. In that sense, the Republican candidate was a spoiler even though leading in first choice support.
The Tideman alternative method avoids this by first eliminating all candidates not in the Smith set or Schwartz set, then performing exactly one round of IRV, repeating this process until a Condorcet candidate appears. Other Condorcet methods also elect from these sets using different rules; Tideman's is the most functionally-similar to IRV.
In practice, IRV does not seem to discourage candidacies. In Australia's House of Representatives elections in 2007, for example, the average number of candidates in a district was seven, and at least four candidates ran in every district; notwithstanding the fact that Australia only has two major political parties. Every seat was won with a majority of the vote, including several where results would have been different under plurality voting. A study of ballot image data found that all of the 138 RCV elections held in four Bay Area cities in California elected the Condorcet winner, including many with large fields of candidates and 46 where multiple rounds of counting were required to determine a winner.
IRV is not a proportional voting method. Like all winner-take-all voting methods, IRV tends to exaggerate the number of seats won by the largest parties; small parties without majority support in any given constituency are unlikely to earn seats in a legislature, although their supporters will be more likely to be part of the final choice between the two strongest candidates. A simulation of IRV in the 2010 UK general election by the Electoral Reform Society concluded that the election would have altered the balance of seats among the three main parties, but the number of seats won by minor parties would have remained unchanged.
Australia, a nation with a long record of using IRV for the election of legislative bodies, has had representation in its parliament broadly similar to that expected by plurality methods. Medium-sized parties, such as the National Party of Australia, can co-exist with coalition partners such as the Liberal Party of Australia, and can compete against it without fear of losing seats to other parties due to vote splitting, although generally in practice these two parties only compete against each other when a sitting member of the coalition leaves Parliament. IRV is more likely to result in legislatures where no single party has an absolute majority of seats (a hung parliament), but does not generally produce as fragmented a legislature as a fully proportional method, such as is used for the House of Representatives of the Netherlands or the New Zealand House of Representatives, where coalitions of numerous small parties are needed for a majority.
The costs of printing and counting ballot papers for an IRV election are no different from those of any other method using the same technology. However, the more-complicated counting system may encourage officials to introduce more advanced technology, such as software counters or electronic voting machines. Pierce County, Washington election officials outlined one-time costs of $857,000 to implement IRV for its elections in 2008, covering software and equipment, voter education and testing.
Because it does not require two separate votes, IRV is assumed to cost less than two-round primary/general or general/runoff election methods. However, in 2009, the auditor of Washington counties reported that the ongoing costs of the system were not necessarily balanced by the costs of eliminating runoffs for most county offices, because those elections may be needed for other offices not elected by IRV. Other jurisdictions have reported immediate cost savings.
Australian elections are counted by hand. The 2010 federal election cost a total of $7.68 per elector of which only a small proportion is the actual counting of votes. Counting is now normally performed in a single pass at the polling center as described above.
The perceived costs or cost savings of adopting an IRV method are commonly used by both supporters and critics. In the 2011 referendum on the Alternative Vote in the UK, the NOtoAV campaign was launched with a claim that adopting the method would cost £250 million; commentators argued that this headline figure had been inflated by including £82 million for the cost of the referendum itself, and a further £130 million on the assumption that the UK would need to introduce electronic voting systems, when ministers had confirmed that there was no intention of implementing such technology, whatever the outcome of the election. Automated vote counting is seen by some to have a greater potential for election fraud; IRV supporters counter these claims with recommended audit procedures, or note that automated counting is not required for the method at all.
John Russo, Oakland City Attorney, argued in the Oakland Tribune on 24 July 2006 that "Instant runoff voting is an antidote to the disease of negative campaigning. IRV led to San Francisco candidates campaigning more cooperatively. Under the method, their candidates were less likely to engage in negative campaigning because such tactics would risk alienating the voters who support 'attacked' candidates", reducing the chance that they would support the attacker as a second or third choice.
In 2013–2014, the Rutgers-Eagleton Poll surveyed more than 4,800 likely voters in 21 cities after their local city elections—half in cities with IRV elections and 14 in control cities selected by project leaders Caroline Tolbert of the University of Iowa and Todd Donovan of Western Washington University. Among findings, respondents in IRV cities reported candidates spent less time criticizing opponents than in cities that did not use IRV. In the 2013 survey, for example, 5% of respondents said that candidates criticized each other "a great deal of the time" as opposed to 25% in non-IRV cities. An accompanying survey of candidates reported similar findings.
Internationally, Benjamin Reilly suggests instant-runoff voting eases ethnic conflict in divided societies. This feature was a leading argument for why Papua New Guinea adopted instant-runoff voting. However, Lord Alexander's objections to the conclusions of the British Independent Commission on the Voting System's report cites the example of Australia saying "their politicians tend to be, if anything, more blunt and outspoken than our own".
In Ann Arbor, Michigan arguments over IRV in letters to newspapers included the belief that IRV "gives minority candidate voters two votes", because some voters' ballots may count for their first choice in the first round and a lesser choice in a later round. The argument that IRV represents plural voting is sometimes used in arguments over the "fairness" of the method, and has led to several legal challenges in the United States. The argument was addressed and rejected by a Michigan court in 1975; in Stephenson v. the Ann Arbor Board of City Canvassers, the court held "majority preferential voting" (as IRV was then known) to be in compliance with the Michigan and United States constitutions, writing:
Under the "M.P.V. System", however, no one person or voter has more than one effective vote for one office. No voter's vote can be counted more than once for the same candidate. In the final analysis, no voter is given greater weight in his or her vote over the vote of another voter, although to understand this does require a conceptual understanding of how the effect of a "M.P.V. System" is like that of a run-off election. The form of majority preferential voting employed in the City of Ann Arbor's election of its Mayor does not violate the one-man, one-vote mandate nor does it deprive anyone of equal protection rights under the Michigan or United States Constitutions.
The same argument was advanced in opposition to IRV in Maine. Governor Paul LePage claimed, ahead of the 2018 primary elections, that IRV would result in "one person, five votes", as opposed to "one person, one vote". In litigation following the results of the 2018 election for Maine's 2nd congressional district, Representative Bruce Poliquin claimed that IRV allowed his opponents to "cast ballots for three different candidates in the same election".
Because the ballot marking is more complex, there can be an increase in spoiled ballots. In Australia, voters are required to write a number beside every candidate, and the rate of spoiled ballots can be five times higher than plurality voting elections. Since Australia has compulsory voting, however, it is difficult to tell how many ballots are deliberately spoiled. Where complete rankings are not required, a ballot may become exhausted if none of the ranked choices on that ballot advance to the next round.
Most jurisdictions with IRV do not require complete rankings and may use columns to indicate preference instead of numbers. In American elections with IRV, more than 99% of voters typically cast a valid ballot.
A 2015 study of four local U.S. elections that used IRV found that ballot exhaustion occurred often enough in each of them that the winner of each election did not receive a majority of votes cast in the first round. The rate of ballot exhaustion in each election ranged from a low of 9.6% to a high of 27.1%. As one point of comparison, the number of votes cast in the 190 regularly scheduled primary runoff elections for the U.S House and U.S. Senate from 1994 to 2016 decreased from the initial primary on average by 39%, according to a 2016 study by FairVote.
The term preferential voting refers to any of a number of voting methods by which, on a single ballot when there are more than two possible choices, the second or less-preferred choices of voters can be taken into account if no candidate or proposition attains a majority. While it is more complicated than other methods of voting in common use, and is not a substitute for the normal procedure of repeated balloting until a majority is obtained, preferential voting is especially useful and fair in an election by mail if it is impractical to take more than one ballot. In such cases, it makes possible a more representative result than under a rule that a plurality shall elect ... Preferential voting has many variations. One method is described here by way of illustration.
The instant-runoff voting method is then detailed. Robert's Rules continues:
The system of preferential voting just described should not be used in cases where it is possible to follow the normal procedure of repeated balloting until one candidate or proposition attains a majority. Although this type of preferential ballot is preferable to an election by plurality, it affords less freedom of choice than repeated balloting, because it denies voters the opportunity of basing their second or lesser choices on the results of earlier ballots, and because the candidate or proposition in last place is automatically eliminated and may thus be prevented from becoming a compromise choice.
Two other books on parliamentary procedure take a similar stance, disapproving of plurality voting and describing preferential voting as an option, if authorized in the bylaws, when repeated balloting is impractical: The Standard Code of Parliamentary Procedure and Riddick's Rules of Procedure.
In Australia, IRV is called preferential voting, which has been used to elect members of the Australian House of Representatives since the 1919 federal election. Ballot papers are marked with the order of preferences: 1, 2, 3, etc. Counting of the ballot papers proceeds and when no candidate receives 50% plus one vote of the first preference vote (candidates with a number one), the candidate with the fewest first preference votes is eliminated and that candidate's votes are distributed to the remaining candidates. The process continues until a candidate accumulates 50% plus one vote, or a simple majority. Counting will continue to finality, which results in what is referred to as the two-party preferred vote, which expresses the electorate's voting preference equivalent to a 2-person election of the two most popular candidates. Most state and council (local government) elections also use the method.
In Canada, IRV is called the alternative vote, which has never been used for federal elections but was used for provincial elections in British Columbia (1952 and 1953), Alberta (1926–1955 in rural districts), and Manitoba (1927–1953).
IRV is used in whole or in part to elect the leaders of the three largest federal political parties in Canada, the Liberal Party of Canada, the Conservative Party of Canada, and the New Democratic Party of Canada, albeit the New Democratic Party uses a mixture of IRV and exhaustive voting, depending on the member. Canadian Prime Minister Stephen Harper won an IRV election to become party leader in the 2004 leadership election. In 2013, the Liberal Party of Canada membership elected Justin Trudeau as party leader through IRV in a national leadership election. In the 2017 Conservative Party of Canada leadership election, the party membership used IRV with weighted voting to elect Andrew Scheer as party leader.
In 2014, the Province of Ontario announced that municipalities would have the option to use IRV for local elections starting in 2018, and authorizing legislation was passed in 2016. London, Ontario subsequently decided to exercise that option 2018.
IRV is used in numerous electoral college environments, including the election of the President of India by the members of the Parliament of India and of the Vidhan Sabhas – the state legislatures.
While most elections in the Republic of Ireland use the single transferable vote (STV), in single-winner contests this reduces to IRV. This is the case in all Presidential elections and Seanad panel by-elections, and most Dáil by-elections In the rare event of multiple simultaneous vacancies in a single Dáil constituency, a single STV by-election may be held; for Seanad panels, multiple IRV by-elections are held.
In New Zealand, IRV is known as the alternative vote or preferential vote, which is used in the elections of mayors and councillors in single-member wards in some cities, such as Dunedin and Wellington. Multi-member wards in these cities use STV.
In the 1992 referendum on the voting method to elect members of the New Zealand House of Representatives, the alternative vote was one of the four alternative methods available (alongside MMP, STV and SM). It came third of the alternative methods (ahead of SM) with 6.6% of the vote. IRV, under the name preferential vote, was one of the four alternative methods choices presented in the 2011 voting method referendum, but the referendum resulted in New Zealanders choosing to keep their proportional method of representation instead, while IRV came last with 8.34%.
In the United Kingdom, IRV is commonly known as the alternative vote, which is used to elect the leaders of the Labour Party and the Liberal Democrats. (The leader of the Conservative Party is elected under a similar method, a variant of the exhaustive ballot.) It is also used for by-elections to the British House of Lords, in which hereditary peers are selected for that body. AV is also used by members of parliament to elect the chairmen of select committees and the Speaker of the House of Lords. The Speaker of the House of Commons is elected by the exhaustive ballot.
In 2010, the Conservative—Liberal Democrat coalition government agreed to hold a national referendum on the alternative vote, held on 5 May 2011. The proposal would have affected the way in which Members of Parliament are elected to the British House of Commons at Westminster. It was only the second national referendum ever to be held within the United Kingdom and the result of the referendum was a decisive rejection of the adoption of the alternative vote by a margin of 67.9% to 32.1% of voters on a national turnout of 42%.
In the United States, IRV is used by several municipalities and other jurisdictions including San Francisco and Oakland, California, and Minneapolis and Saint Paul, Minnesota. United States private associations that use IRV include the Hugo Awards for science fiction, the Academy of Motion Picture Arts and Sciences in selection of the Oscar for Best Picture, and more than fifty colleges and universities for student elections.
Maine became the first U.S. state to approve IRV for its primary and general elections for governor, U.S. Senate, U.S. House and state legislature, in a 2016 referendum. The state supreme court ruled this method of voting was unconstitutional for state general elections, but this ruling did not affect primary and federal elections. The state legislature attempted to repeal IRV for all elections unless the state constitution was amended, but this repeal was put on hold by a people's veto petition. The June 2018 primary election both used IRV to determine party candidates and Maine Question 1 passed, which blocked the repeal. Democrat Jared Golden became the first congressional candidate in the United States to win a general election as a result of IRV, defeating incumbent Republican Bruce Poliquin in second round balloting for Maine's 2nd congressional district in 2018. In the future, IRV will also be used for primary elections for federal elections and only primary elections for state offices.
The term instant runoff voting is derived from the name of a class of voting methods called runoff voting. In runoff voting voters do not rank candidates in order of preference on a single ballot. Instead a similar effect is achieved by using multiple rounds of voting. All multi-round runoff voting methods allow voters to change their preferences in each round, incorporating the results of the prior round to influence their decision. This is not possible in IRV, as participants vote only once, and this prohibits certain forms of tactical voting that can be prevalent in 'standard' runoff voting.
A method closer to IRV is the exhaustive ballot. In this method—one familiar to fans of the television show American Idol—one candidate is eliminated after each round, and many rounds of voting are used, rather than just two. Because holding many rounds of voting on separate days is generally expensive, the exhaustive ballot is not used for large-scale, public elections.
The simplest form of runoff voting is the two-round system, which typically excludes all but two candidates after the first round, rather than gradually eliminating candidates over a series of rounds. Eliminations can occur with or without allowing and applying preference votes to choose the final two candidates. A second round of voting or counting is only necessary if no candidate receives an overall majority of votes. This method is used in Mali, France and the Finnish and Slovenian presidential election.
The contingent vote, also known as Top-two IRV, or batch-style, is the same as IRV except that if no candidate achieves a majority in the first round of counting, all but the two candidates with the most votes are eliminated, and the second preferences for those ballots are counted. As in IRV, there is only one round of voting.
Under a variant of contingent voting used in Sri Lanka, and the elections for Mayor of London in the United Kingdom, voters rank a specified maximum number of candidates. In London, the Supplementary Vote allows voters to express first and second preferences only. Sri Lankan voters rank up to three candidates for the President of Sri Lanka.
While similar to "sequential-elimination" IRV, top-two can produce different results. Excluding more than one candidate after the first count might eliminate a candidate who would have won under sequential elimination IRV. Restricting voters to a maximum number of preferences is more likely to exhaust ballots if voters do not anticipate which candidates will finish in the top two. This can encourage voters to vote more tactically, by ranking at least one candidate they think is likely to win.
Conversely, a practical benefit of 'contingent voting' is expediency and confidence in the result with only two rounds. Particularly in elections with few (e.g., fewer than 100) voters, numerous ties can destroy confidence. Heavy use of tie-breaking rules leaves uncomfortable doubts over whether the winner might have changed if a recount had been performed.
IRV may also be part of a larger runoff process:
The common feature of these IRV variations is that one vote is counted per ballot per round, with rules that eliminate the weakest candidate(s) in successive rounds. Most IRV implementations drop the requirement for a majority of cast ballots.
In San Francisco, ranked-choice voting is sometimes called 'instant run-off voting.' The Department of Elections generally uses the term ranked-choice voting, because it describes the voting method – voters are directed to rank their first-, second- and third-choice candidates. The Department also uses the term ranked-choice voting because the word 'instant' might create an expectation that final results will be available immediately after the polls close on election night.
This format allows a voter to select a first-choice candidate in the first column, a second-choice candidate in the second column, and a third-choice candidate in the third column.
the 2009 election suffered from not only the 'thwarted majorities' or Condorcet's paradox, but also the 'no-show paradox' that shows that Wright voters who preferred Montroll over Kiss (that is, ranked Montroll 2nd) would have been better staying home and not voting at all.
Montroll was favored over Republican Kurt Wright 56% to 44% ... and over Progressive Bob Kiss 54% to 46% ... In other words, in voting terminology, Montroll was a 'beats-all winner,' also called a 'Condorcet winner' ... However, in the IRV election, Montroll came in third!
This is an IRV failure. The IRV result is clearly not what people actually wanted. More people liked Montroll over Kiss than the other way around, but IRV elected the loser.
Montroll would have beaten any other candidate in a one-on-one election.
successfully prevented the election of the candidate who would likely have won under plurality rules, but would have lost to either of the other top finishers in a runoff
Montroll was the 'Beats-All winner' (aka the 'Condorcet winner') as he would have beaten both Wright (56% to 44%) and Kiss (54% to 46%) in head-to-head races, demonstrating that he was the preferred candidate by the majority of voters.
What is the best way to vote strategically? The best strategic vote is to number the candidates in the order you would like to see them elected. ... in electorate of more than 90,000 voters, and without perfect knowledge, such a strategy is not possible.
IRV can perform better than plurality voting provided there are many honest voters. (In the unlikely case that everyone votes strategically, the two methods are tied.)
IRV removes the "spoiler effect" whereby minor party or independent candidates knock off major party candidates, increasing the choices available to the voters.
IRV completely eliminates the 'spoiler' effect – that is, votes split between a weak and a strong candidate won't cause the strong candidate to lose if s/he is the second choice of the weak candidate's voters.
Instant-runoff voting ends the spoiler effect forever
Alternative Vote: Stops the Spoiler Effect
Candidates C and D spoiled the election for B ... With them in the running, A won, whereas without them in the running, B would have won. ... Instant runoff voting ... does not do away with the spoiler problem entirely, although it ... makes it less likely
IRV is excellent for preventing classic spoilers-minor candidates who irrationally tip the election from one major candidate to another. It is not so good when the 'spoiler' has a real chance of winning
After a minor party is strong enough to win, on the other hand, a vote for them could have the same spoiler effect that it could have under the current plurality system
IRV means betraying your true favorite third party candidate pays off. Voting third party can mean wasting your vote under IRV, just like under plurality.
They'll have a strategic incentive to falsify their preferences.
The city of Burlington, Vermont held a mayoral election on March 3, 2009, the second election since the city approved instant-runoff voting (IRV) for use in mayoral elections in 2005. The incumbent mayor Bob Kiss, who had served since 2006, ran for reelection as the VT Progressive candidate.Unlike Burlington's first IRV mayoral election in 2006, the IRV winner in 2009 (VT Progressive candidate Bob Kiss) was neither the same as the plurality winner (Republican candidate Kurt Wright) nor the Condorcet winner (Democratic candidate Andy Montroll).The results focused attention on the IRV method,. A citizen's initiative led by backers of Kurt Wright resulted in the repeal of IRV in March 2010 by a vote of 52% to 48%.2009 Minneapolis mayoral election
The 2009 Minneapolis mayoral election was held on November 3, 2009 to elect the Mayor of Minneapolis for a four-year term. Incumbent R. T. Rybak won re-election for a third term in the first round with 73.6% of the vote.
This was the first mayoral election in the city's history to use instant-runoff voting, popularly known as ranked choice voting. Voters had the option of ranking up to three candidates. Municipal elections in Minnesota are nonpartisan, although candidates were able to identify with a political party on the ballot.Ballot Access News
Ballot Access News is a United States-based monthly online and print newsletter edited and published by Richard Winger of California, an expert on ballot access law in the United States. Published since 1985, the newsletter advocates "fair and equitable ballot access laws."
Ballot Access News reports on state and federal court decisions, compares American ballot access laws to those of other democratic nations, and documents the number of votes independent and minor party candidates receive. The newsletter also records the activities of the Coalition for Free and Open Elections, an interest group of minor party members and others working together on ballot access law reform issues. Further, the newsletter occasionally notes developments on the usage of instant-runoff voting in the United States.Contingent vote
The contingent vote (also Top-two IRV) is an electoral system used to elect a single winner. It is a variation of instant-runoff voting, in which the voter ranks the candidates in order of preference.
If no candidate receives an absolute majority of first preference votes, then all but the two leading candidates are eliminated and there is a second count. In the second count, the votes of those who supported eliminated candidates are distributed among the two remaining candidates, so that one candidate achieves an absolute majority.
The contingent vote differs from the alternative vote which allows for many rounds of counting, eliminating only one weakest candidate each round.
The contingent vote can also be considered a compressed form of the two round system (runoff system), in which both 'rounds' occur without the need for voters to go to the polls twice.
Today, a special variant of the contingent vote is used to elect the President of Sri Lanka. Another variant, called the supplementary vote, is used to elect mayors and Police and Crime Commissioners in England. In the past the ordinary form of the contingent vote was used to elect the Legislative Assembly of Queensland from 1892 to 1942. To date, this has been the longest continuous use of the system anywhere in the world. It was also used in the US state of Alabama in the 1920s.Coombs' method
Coombs' method (or the Coombs rule) is a ranked voting system created by Clyde Coombs used for 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.Electoral reform in Maryland
Electoral reform in Maryland refers to efforts, proposals and plans to change the election and voting laws in Maryland. In 2007, Maryland became the first U.S. state to join the National Popular Vote Interstate Compact. Bills have also been introduced to implement instant runoff voting (IRV) statewide, but they have failed, largely due to legislators' concerns about complicating the election process and causing technical problems similar to those encountered by Florida during the 2000 U.S. Presidential election. However, Takoma Park, Maryland adopted IRV in 2006 after it won 84% approval in an advisory ballot measure on November 8, 2005. Maryland is the home of the electoral reform organization Fairvote. In 2007, Maryland's Board of Elections Administrator, Linda Lamone, was quoted in Diebold advertising literature.Electoral reform in Michigan
Electoral reform in Michigan refers to efforts, proposals and plans to change the election and voting laws of Michigan. In 2004, Ferndale residents overwhelmingly passed Proposal B, implementing instant-runoff voting. Ballot access laws in Michigan are rather restrictive, as they currently requires a political party to submit 38,024 signatures, including 100 signatures from half of all Michigan Congressional districts. The Michigan Third Parties Coalition is seeking to relax those requirements. So far, no bills have been introduced in the Michigan Legislature to join the National Popular Vote Interstate Compact.Electoral reform in North Carolina
Electoral reform in North Carolina refers to efforts to change the voting and election laws in the Tar Heel State.Exhaustive ballot
The exhaustive ballot is a voting system used to elect a single winner. Under the exhaustive ballot the elector simply casts a single vote for their chosen candidate. However, if no candidate is supported by an overall majority of votes then the candidate with the fewest votes is eliminated and a further round of voting occurs. This process is repeated for as many rounds as necessary until one candidate has a majority.
The exhaustive ballot is similar to the two-round system but with key differences. Under the two round system if no candidate wins a majority on the first round, only the top two recipients of votes advance to the second (and final) round of voting, and a majority winner is determined in the second round. By contrast, on the exhaustive ballot only one candidate is eliminated per round; thus, several rounds of voting may be required until a candidate reaches a majority. (In some circumstances, the two or more lowest candidates can be eliminated simultaneously if together they have fewer votes than the lowest candidate above them. In other words, this "bulk exclusion" cannot change the order of elimination, unlike a two-round system.)
Because voters may have to cast votes several times, the exhaustive ballot is not used in large-scale public elections. Instead it is usually used in elections involving, at most, a few hundred voters, such as the election of a prime minister or the presiding officer of an assembly. The exhaustive ballot is currently used, in different forms, to elect the members of the Swiss Federal Council, the First Minister of Scotland, the President of the European Parliament, and the speakers of the House of Commons of Canada, the British House of Commons and the Scottish Parliament, the various party nominees for President of the United States, the host city of the Olympic Games and the host of the FIFA World Cup, and, formerly, to elect the President and the State Comptroller of Israel, which are now elected – though still indirectly by the Knesset – using a two-round system.History and use of instant-runoff voting
Instant-runoff voting (IRV) is a voting method used in single-seat elections with more than two candidates. Instead of voting only for a single candidate, voters in IRV elections can rank the candidates in order of preference. Ballots are initially counted for each elector's top choice, losing candidates are eliminated, and ballots for losing candidates are redistributed until one candidate is the top remaining choice of a majority of the voters. When the field is reduced to two, it has become an "instant runoff" that allows a comparison of the top two candidates head-to-head.
IRV more commonly known outside the US as the alternative vote or preferential voting, was devised around 1870 by the US architect W. R. Ware. Today it is in use at a national level to elect the Australian House of Representatives, the National Parliament of Papua New Guinea, the President of Ireland and President of India. In Australia it is also used for elections to the legislative assemblies (lower houses) of all states and territories except Tasmania and the Australian Capital Territory, and for the Tasmanian Legislative Council (upper house).
IRV is also used a number of municipal elections in Australia, the United States, United Kingdom and New Zealand. Because of its relationship to the Single Transferable Vote (STV) system, IRV is used for by-elections in a some jurisdictions that use STV for ordinary parliamentary elections, such as the Republic of Ireland and Scotland.
IRV is known by different names in the various countries in which it is used. It is also known as the 'Alternative Vote', 'Ranked Choice Voting', and 'Preferential Voting', although IRV is only one of a number of forms of preferential voting systems.Instant-runoff voting in the United States
Instant-runoff voting (IRV) is used for state and congressional elections in Maine and for local elections in 11 cities, where it is often called "ranked-choice voting." Those cities include San Francisco, California; Oakland, California; Berkeley, California; San Leandro, California; Takoma Park, Maryland; Basalt, Colorado; Telluride, Colorado; St. Paul, Minnesota; Minneapolis, Minnesota; Santa Fe, New Mexico, and Portland, Maine. It is pending implementation in several additional cities, including in 2019 in Las Cruces, New Mexico and St. Louis Park, Minnesota. IRV is commonly used for student government and other non-governmental elections.Between 1912 and 1930, limited forms of IRV (typically with only two rankings) were implemented and subsequently repealed in the states of Florida, Indiana, Maryland, Minnesota, and Wisconsin. In the 1970s, it was implemented and repealed in Ann Arbor, Michigan. More recently, it was adopted and repealed in Pierce County, Washington (2006-2009); Burlington, Vermont (2005-2010); Aspen, Colorado (2007-2010); and in North Carolina, which allowed its use in elections between 2006 and 2013.
In 2016, voters in Maine approved an initiative to become the first state to use IRV statewide in elections for governor, state legislature, U.S. Senate, and U.S. House. Despite efforts by the state legislature and state supreme court to delay the implementation of IRV, a "people's veto" referendum campaign kept the IRV law in place, with the state supreme court ruling that IRV would be introduced for the primary on June 12, 2018. In that election, Maine voters re-affirmed implementation of IRV by popular referendum while using IRV for the first time in primaries for the offices of governor, U.S. House, and state legislator.In November 2018, an instant runoff took place in the election for Maine's 2nd congressional district. The Republican incumbent Bruce Poliquin led the first-round count by 2,171 votes, but Democratic candidate Jared Golden won with a majority of 3,509 votes in the final round count after votes for independent candidates Tiffany Bond and Will Hoar were added to the totals of the top two candidates.Monotonicity criterion
The monotonicity criterion is a voting system criterion used to evaluate both single and multiple winner ranked voting systems. A ranked voting system is monotonic if it is neither possible to prevent the election of a candidate by ranking them higher on some of the ballots, nor possible to elect an otherwise unelected candidate by ranking them lower on some of the ballots (while nothing else is altered on any ballot).
In single winner elections that is to say no winner is harmed by up-ranking and no loser can win by down-ranking. Douglas R. Woodall called the criterion mono-raise.
Raising a candidate x on some ballots while changing the orders of other candidates does not constitute a failure of monotonicity. E.g., harming candidate x by changing some ballots from z > x > y to x > y > z isn't a violation of the monotonicity criterion.
The monotonicity criterion renders the intuition that there should be neither need to worry about harming a candidate by (nothing else than) up-ranking nor it should be possible to support a candidate by (nothing else than) counter-intuitively down-ranking. There are several variations of that criterion; e.g., what Douglas R. Woodall called mono-add-plump: A candidate x should not be harmed if further ballots are added that have x top with no second choice. Agreement with such rather special properties is the best any ranked voting system may fulfill: The Gibbard–Satterthwaite theorem shows, that any meaningful ranked voting system is susceptible to some kind of tactical voting, and Arrow's impossibility theorem shows that individual rankings can't be meaningfully translated into a community-wide ranking where the order of candidates x and y is always independent of irrelevant alternatives z. Noncompliance with the monotonicity criterion doesn't tell anything about the likelihood of monotonicity violations, failing in one of a million possible elections would be as well a violation as missing the criterion in any possible election.
Of the single-winner ranked voting systems, Borda, Schulze, ranked pairs, maximize affirmed majorities, descending solid coalitions, and descending acquiescing coalitions are monotonic, while Coombs' method, runoff voting, and instant-runoff voting (IRV) are not.
Most variants of the single transferable vote (STV) proportional representations are not monotonic, especially all that are currently in use for public elections (which simplify to IRV when there is only one winner).
All plurality voting systems are monotonic if the ballots are treated as rankings where using more than two ranks is forbidden. In this setting first past the post and approval voting as well as the multiple-winner systems single non-transferable vote, plurality-at-large voting (multiple non-transferable vote, bloc voting) and cumulative voting are monotonic. Party-list proportional representation using D'Hondt, Sainte-Laguë or the largest remainder method is monotonic in the same sense.
In elections via the single-winner methods range voting and majority judgment nobody can help a candidate by reducing or removing support for them. The definition of the monotonicity criterion with regard to these methods is disputed. Some voting theorists argue that this means these methods pass the monotonicity criterion; others say that, as these are not ranked voting systems, they are out of the monotonicity criterion's scope.Optional preferential voting
Optional preferential voting (OPV) is a type of preferential voting system under which voters indicate the order of their preferences by numbers. Full-preferential voting requires a preference to be indicated for each candidate. Under OPV voters may choose to mark a preference for as many candidates as they want. Although complete numbering is not required under OPV, single-preference voters may be required to use a '1' rather than a tick or cross. Some jurisdictions allow ticks or crosses as the voter's intention is clear. Some jurisdictions use semi-optional preferential voting, when a minimum number of preferences are required to be expressed.
OPV is used in elections in New South Wales and the Northern Territory, Australia. It was used in Queensland from 1992 to 2015.In both the Tasmanian House of Assembly and the Tasmanian Legislative Council, semi-optional voting is used, with a minimum number of preferences required to be expressed; but there is no requirement to complete the entire ballot paper. Elections for all other Australian lower houses use full-preferential voting. In the Victorian Legislative Council, semi-optional voting is used if a voter chooses to vote below the line. Voting above the line requires only a ‘1’ being placed in one box, and group voting tickets voting has applied since 1988.The Australian Senate voting reform of 2016 switched from full-preferential voting to semi-optional. A minimum number is specified in the instructions on the ballot paper. Since in the past a single number '1' above the line was formal, that is still a valid vote even though voters are encouraged to number six squares.
In other countries, such as Malta, the Republic of Ireland, and Northern Ireland, full preferences are not required.
The "ranked-choice voting" system used by Maine, USA, can be considered optional-preferential as voters are allowed to rank just one candidate. The system also allows voters to "skip" one ranking (e.g. marking a first choice and a third choice, but not a second choice). In that case, the next ranking would be advanced to the next highest ranking.Preferential voting
Preferential voting or preference voting may refer to different election systems or groups of election systems. European literature mainly uses the term for open list proportional representation, Australian literature for Single Transferable Vote or for Ranked voting, and American literature for any of them. Recently, an increasing number of authors, including David Farrell, Ian McAllister and Jurij Toplak, see preferentiality as one of the characteristics by which electoral systems can be evaluated. According to this view, all electoral methods are preferential, but to different degrees and may even be classified according to their preferentiality. Preferential voting, when understood as one of the systems or a group of systems, may refer, among other, to:
Ranked voting methods, all election methods that involve ranking candidates in order of preference
Optional preferential voting
Instant-runoff voting, referred to as "preferential voting" in Australia and as "ranked choice voting" in United States, is one type of ranked voting method.
Single transferable vote
Score voting, in which voters assign points to each candidate
Open list, sometimes known as "preferential voting" in Europe and nations such as Sri Lanka
Bucklin voting, which was sometimes known as "preferential voting" when used in the United StatesRanked voting
Ranked voting describes certain voting systems in which voters rank outcomes in a hierarchy on the ordinal scale (ordinal voting systems). In some areas ranked-choice voting is called preferential voting, but in other places this term has various other meanings.When choosing among more than two options, preferential ballots collect more information from voters than first-past-the-post voting (plurality voting). This does not mean that preferential voting is intrinsically better. Arrow's impossibility theorem and Gibbard's theorem prove that all voting systems must make trade-offs between desirable properties. There is, accordingly, no consensus among academics or public servants as to the best electoral system. The other major branch of voting systems are cardinal voting systems, where candidates are independently rated, rather than relatively ranked.
There are many types of preferential voting, with several used in governmental elections: Instant-runoff voting is employed in Australian state and federal elections, in Ireland for its presidential elections, and by some jurisdictions in the United States, United Kingdom, and New Zealand. The single transferable vote is used for national elections in the Republic of Ireland and Malta, the Australian Senate, for regional and local elections in Northern Ireland, for all local elections in Scotland, and for some local elections in New Zealand and the United States. Borda count is used in Slovenia and Nauru. Contingent vote and Supplementary vote are also used in a few locations. Condorcet methods have found more use among private organizations and minor parties.Resolvability criterion
Resolvability criterion can refer to any voting system criterion that ensures a low possibility of tie votes.
In Nicolaus Tideman's version of the criterion, for every (possibly tied) winner in a result, there must exist a way for one added vote to make that winner unique.
Douglas R. Woodall's version requires that the proportion of profiles giving a tie approaches zero as the number of voters increases toward infinity.Methods that satisfy both versions include approval voting, range voting, Borda count, instant-runoff voting, minimax Condorcet, plurality, Tideman's ranked pairs, and Schulze.Methods that violate both versions include Copeland's method and the Slater rule.Reversal symmetry
Reversal symmetry is a voting system criterion which requires that if candidate A is the unique winner, and each voter's individual preferences are inverted, then A must not be elected. Methods that satisfy reversal symmetry include Borda count, the Kemeny-Young method, and the Schulze method. Methods that fail include Bucklin voting, instant-runoff voting and Condorcet methods that fail the Condorcet loser criterion such as Minimax.
For cardinal voting systems which can be meaningfully reversed, approval voting and range voting satisfy the criterion.Two-party-preferred vote
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 highest two candidates, who in some cases can be independents. 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 the 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 not informative. TPP results above seat-level, such as a national or statewide TPP, are also informative only and have no direct effect on the election outcome.
The full allocation of preferences under instant-runoff voting is used in the lower houses of the Federal, Queensland, Victorian, Western Australian, South Australian, and Northern Territory parliaments, as well as the upper house of Tasmania. The New South Wales lower house uses 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.Two-round system
The two-round system (also known as the second ballot, runoff voting or ballotage) is a voting method used to elect a single winner, where the voter casts a single vote for their chosen candidate. However, if no candidate receives the required number of votes, then those candidates having less than a certain proportion of the votes, or all but the two candidates receiving the most votes, are eliminated, and a second round of voting is held.
The two-round system is used around the world for the election of legislative bodies and directly elected presidents. For example, it is used in French presidential, legislative, and departmental elections. In Italy, it is used to elect mayors, but also to decide which party or coalition receives a majority bonus in city councils. A two-round system is used also to elect the presidents of Afghanistan, Argentina, Austria, Benin, Brazil, Bulgaria, Burkina Faso, Cape Verde, Chile, Colombia, Costa Rica, Croatia, Czech Republic, Cyprus, Dominican Republic, East Timor, Ecuador, Egypt, El Salvador, Finland, Ghana, Guatemala, Haiti, India, Indonesia, Kyrgyzstan, Liberia, North Macedonia, Peru, Poland, Portugal, Romania, Russia, Senegal, Serbia, Slovakia, Slovenia, Turkey, Ukraine, Uruguay and Zimbabwe. Historically it was used to elect the Reichstag in the German Empire between 1871 and 1918, and in New Zealand in the 1908 and 1911 elections.
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"At present, the UK uses the “first past the post” system to elect MPs to the House of Commons. Should the “alternative vote” system be used instead?"