Instant-runoff voting

For other types of run-off voting systems, see Run-off voting.

Example Instant runoff voting ballot

Instant runoff voting (also known as the Alternative Vote, AV, and ranked choice voting) is a form of preferential voting. It is a voting system in which voters rank candidates in order of preference, most commonly in single-winner elections. Indeed, IRV can be considered a special case of single transferable vote for the case where there is a single position to be filled. If no candidate is the first preference of a majority of voters, the candidate with the fewest number of first preference rankings is eliminated and that candidate's ballots are redistributed at full value to the remaining candidates according to the next ranking on each ballot. This process is repeated until one candidate obtains a majority of votes among candidates not eliminated. The term instant runoff is used because the method is said to simulate a series of runoff elections tallied in rounds, as in an exhaustive ballot election. In the contingent vote form of IRV, all but the top vote-getters are eliminated before the instant runoff.

Instant runoff voting is used to elect members of the Australian House of Representatives, the President of Ireland, the national parliament of Papua New Guinea, and the Fijian House of Representatives. IRV is employed by several jurisdictions in the United States, including San Francisco and Oakland in California and Minneapolis and St. Paul in Minnesota. It is used to elect the leaders of the Labour Party and the Liberal Democrats in the United Kingdom and the leader of the Liberal Party of Canada in a national primary and in the elections of city mayors in a number of countries including the United Kingdom (in the variant known as Supplementary Vote) and New Zealand.

Many large private associations use IRV, including the Hugo Awards for science fiction and the Academy of Motion Picture Arts and Sciences in selection of best picture.

History

Main article: History and use of instant-runoff voting

Instant runoff voting was invented in 1871 by American architect William Robert Ware. He evidently based IRV on the single-winner outcome of the single transferable vote, originally developed by Carl Andrae and Thomas Hare.

Terminology

In the United States, instant runoff voting is an umbrella term associated with ranked choice elections where there are rounds of counting designed to determine majority winners, low vote-getters are eliminated between rounds, and ballots count for the top-ranked candidate not yet eliminated. The term "instant runoff" is used because the method is said to simulate a series of runoff elections tallied in rounds, as in an exhaustive ballot election, except voters may not tactically change their votes between rounds.

Instant runoff voting has a number of other names, often tied to countries where it is used. In the United States, most observers call it instant runoff voting because of its resemblance to runoff voting, but others use "ranked choice voting" because of the ballot type. It is sometimes referred to as the Alternative Vote (its oldest name) in the United Kingdom and the preferential ballot or preferential voting in Canada and Australia. It has occasionally been referred to as Ware's method, after its U.S. proponent, William Robert Ware.

North Carolina law uses "instant runoff" to describe the contingent vote or "batch elimination" form of IRV in one-seat elections where there is a single second round of counting with the top two candidates advance to the runoff. Election officials in Hendersonville (NC) use "instant runoff" to describe a multi-seat election system that attempts to simulate in a single round of voting their previous system 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 ballots before the first round of a runoff that then are counted in a runoff election.

When the single transferable vote (STV) system is applied to a single-winner election it becomes the same as IRV. For this reason IRV is sometimes considered to be merely a special form of STV. However, because STV was designed for multi-seat constituencies, many scholars consider it to be a separate system from IRV, and that is the convention followed in this article. IRV is usually known simply as "STV" in New Zealand and Ireland, although the term Alternative Vote is also used in those countries.

Multiseat variations of the IRV elimination process, such as Single Transferable Vote, have sometimes been labeled as instant runoff voting although they should be more accurately called preferential bloc voting, since in bloc voting, multiple votes are counted per ballot at the same time.

Election procedure

Optical scan IRV ballot

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, using an 'ascending' system.

The fundamental mechanics of the process are the same regardless of how many candidates the voter ranks, and how many are left unsorted. In some implementations of IRV, the voter is allowed to rank as many or as few choices as they wish, while in other implementations the voter is required to rank either all of the candidates, or only a prescribed number of them.

File:IRV counting flowchart.1.png

Flowchart for counting IRV votes

In the initial count, the first preferences of each voter are counted and used to order the candidates. Each first preference is counted as one vote for the appropriate candidate. If, once all the first preferences are counted, one candidate holds a majority of the votes, that candidate can be immediately declared the winner. Otherwise the candidate who holds the fewest first preferences is eliminated. If there is an exact tie for last place in numbers of votes, special tie-breaking rules are invoked to determine which candidate to eliminate. Some jurisdictions eliminate more than one lowest-ranking candidate simultaneously if their combined number of votes is fewer than the number of votes received by any of the remaining candidates.

Once a candidate has been eliminated, all the ballots assigned to that candidate are recounted and the second preference of each voter is used to reassign their vote to one of the remaining candidates. The total counts for the remaining candidates are updated and the candidates are reordered. Again if the top candidate attains a majority, that candidate is declared the winner, otherwise the bottom candidate is again eliminated and those votes reassigned; each ballot paper is reassigned to whichever remaining candidate is the most preferred by that voter. If a ballot has all its ranked candidates eliminated, it is 'exhausted' and it can no longer be counted towards any candidate. Eventually, one candidate must attain a majority of votes cast for continuing candidates and is declared the winner.

Examples

See also: IRV implementations in United States § Burlington results 2006

Candidate	Round 1		Round 2
Bob Kiss	3,809	(38.9%)	4,761	(48.6%)
Hinda Miller	3,106	(31.7%)	3,986	(40.7%)
Kevin Curley	2,609	(26.7%)	—
Other	254	(2.6%)	—
Exhausted ballots	10	(0.1%)	1,041	(10.5%)
Total	9,778	(100%)	9,778	(100%)

In 2006 the U.S. city of Burlington, Vermont, held a mayoral election using instant runoff voting. Progressive Bob Kiss won in two rounds with 48.6% of the first round ballots, defeating Democrat Hinda Miller who achieved 40.7%. 10.6% of the ballots were exhausted before the final round, with those voters (largely backers of Republican Curley) offering no preference between the final two candidates, Miller and Kiss.

After the first round, Curley and all of the 'other' candidates were eliminated, as their combined vote (2,863) was less than Miller's and so it would be impossible for Curley to pull ahead of Miller, even if he gained every one of the votes from the 'other' candidates. The votes for these candidates were recounted and redistributed between Kiss and Miller; 1,031 of those votes did not express a preference for either remaining candidate, and so were exhausted. After the second round recount, Kiss was declared the winner as he had obtained a majority (54.4%) of the remaining unexhausted ballots.

Irish presidential election, 1990
Candidate	Round 1		Round 2
Mary Robinson	612,265	(38.9%)	817,830	(51.6%)
Brian Lenihan	694,484	(44.1%)	731,273	(46.2%)
Austin Currie	267,902	(17.0%)	—
Exhausted ballots	9,444	(0.6%)	34,992	(2.2%)
Total	1,584,095	(100%)	1,584,095	(100%)

The result of the Irish Presidential election in 1990 is a good example of how instant runoff voting can produce a different result than the simple first past the post system. The three candidates were Brian Lenihan of the traditionally dominant Fianna Fáil party, Austin Currie of the nation's second largest party, Fine Gael, and Mary Robinson of the Labour Party and Worker's 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 over 80% of Currie's votes, being the second preference of the majority of his supporters, thereby overtaking Lenihan, securing majority support and becoming the seventh President of Ireland.

Ballots

As seen above, voters in an IRV election rank candidates on a preferential ballot. IRV systems 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 elections such as those for the President of Ireland and the New South Wales Legislative Assembly, voters are permitted to rank as many or as few candidates as they wish. This is known in Australia as optional preferential voting.

Under optional preferential voting, some voters may rank only the candidates of a single party, or of their most preferred parties. Some voters may 'bullet vote', expressing only a first choice. Allowing voters to rank only as many candidates as they wish grants them greater freedom but can also lead to some voters ranking so few candidates that their vote eventually becomes 'exhausted' – that is, at a certain point during the count it can no longer be counted for a continuing candidate and therefore loses an opportunity to influence the result.

To prevent exhausted ballots, some IRV systems require or request that voters give a complete ordering of all of the candidates in an election – if a voter does not rank all candidates their ballot may be considered spoilt. In Australia this variant is known as 'full preferential voting'. However, when there is a large set of candidates this requirement may prove burdensome and can lead to 'donkey voting' in which, where a voter has no strong opinions about his or her lower preferences, the voter simply chooses them at random or in top-to-bottom order. Partly to overcome these problems, in elections to the Australian House of Representatives many parties distribute 'how-to-vote' cards, recommending how to allocate preferences on the ballot paper.

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. Robson Rotation is a system where the order of candidates on the paper is randomly changed for each print run of the same election's ballot papers.

Voters

Voters have the option to rank candidates in order of choice rather than mark a single candidate. By choosing not to rank all candidates, a voter's ballot may not be counted in the decisive round of counting. Only ballots ranking at least one of the finalists will be counted.

Where preferential voting is used for the election of an assembly or council, parties and candidates often advise their supporters on how to use their lower preferences. As noted above, in Australia parties even issue 'how-to-vote' cards to the electorate before polling day, and Australia's requirement that voters must rank all candidates contributes to some voters using them. These kinds of recommendations can increase the influence of party leaderships and lead to a form of pre-election bargaining, in which smaller parties bid to have key planks of their platforms included in those of the major parties by means of 'preference deals'.

Counting methods

A hand count is possible under IRV. Several nations count ballots by hand. This was the method used in the Cary, North Carolina pilot program in October 2007 (after initially counting first choices on optical scan equipment at the polls), and is used in most non-U.S. jurisdictions; however it is usually more time-consuming than a plurality count, and may need to occur over a number of rounds.

In Australia, a simplified count is sent to a central location on the night with the actual ballot papers transported there, securely, for the final count. In Ireland's presidential race, there are several dozen counting centers around the nation. Each center reports its totals for each candidate and receives instructions from the central office about which candidate or candidates to eliminate in the next round of counting.

IRV has been implemented in U.S. cities using optical scan voting systems, such as San Francisco, California, and Burlington, Vermont.

Winner-take-all single-seat elections vs. legislative elections

The intention of IRV is to find one candidate acceptable to a majority of voters. It is intended as an improvement on the 'First Past the Post' (plurality) voting system. Under 'First Past the Post' the candidate with most votes (a plurality) wins, even if they do not have a majority (more than half) of votes (unless election rules require a runoff under that condition).

IRV is most suited to elections in which there can be only one winner, such as a mayor or governor. Legislative bodies, city councils or boards also often elect winners by dividing voters into geographic districts.

Australia is the only nation with a long record of using IRV for the election of legislative bodies. IRV produces representation very similar to those produced by the plurality system, with a result similar to a two party system in parliament like those found in many countries that use plurality and two-round systems. A significant difference is that a smaller third party, the National Party of Australia, can co-exist with its coalition partner the Liberal Party of Australia, and can compete against it without fear of losing seats to other parties due to vote splitting. In the November 2007 elections, at least four candidates ran in every constituency, with an average of seven, but every constituency was won with an absolute majority of votes.

If IRV is used to elect a city council or legislature, it will not produce proportional representation (PR). This means that it is likely to lead to the representation of a small number of larger parties in an assembly, rather than a proliferation of small parties. Under a parliamentary system it is more likely to produce single party governments than are PR systems, which tend to produce coalition governments. While IRV is designed to ensure that each individual candidate elected is supported by a majority of those in his or her constituency, if used to elect an assembly it does not ensure this result on a national government level. As in other non-PR systems the party or coalition that wins a majority of seats will sometimes not have the support of an overall majority of voters across the nation.

Many election reformers do not advocate IRV for legislative bodies or city councils that are intended to represent both majorities and minorities (in appropriate proportions). As with any winner-take-all election method, IRV can result in a shut-out of minority representation. Gerrymandering of single seat districts can also result in minorities gaining majority control of a legislative body, with IRV or any other winner-take-all election method.

According to a 2007 Brookings Institution paper examining voting behavior in the United States, IRV can empower moderate voters. Presumably, this effect would result from combining the primary and general election into a single election that would have higher participation rates by moderates than typical primaries. However, empirical evidence suggests that IRV does not always favor moderates. A 2006 study found that "Fiji's objective of ameliorating ethnic divisions by the adoption of [IRV] was not successful"; the moderate parties would have fared better under PR.

IRV compared to plurality or two-round runoff voting

Potential advantages of IRV

Tactical voting

In his book Collective Decisions and Voting Nicolaus Tideman uses real-world voting data to analyze all proposed election methods in terms of resistance to tactical voting, and states on page 194 that "the alternative vote [IRV] is quite resistant to strategy." Instant runoff voting reduces incentive for insincere voting by reducing the spoiler effect in cases where there are two major candidates and one or more minor candidates. Under the common plurality ("first past the post") voting system, voters may have an incentive to vote insincerely for one of the two major candidates, instead of their true favorite, because a vote for the favorite is likely to be "wasted."

Usually allows one ballot to determine a majority winner

Robert's Rules of Order calls preferential voting "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 that under a rule that a plurality shall elect. . . . Preferential voting has many variations." The single transferable vote technique used by IRV is the example given."

As for having a true majority, voters who do not rank all the candidates are similar to voters who stay home on election day when there is a two candidate race.

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 in last place is automatically eliminated and may thus be prevented from becoming a compromise choice.

Ranked choice ballots allow a simulated runoff process to eliminate candidates without asking voters again for their top remaining choice. The process logically must end in a majority winner (or a tie) when two final candidates remain, the winner having a majority of votes in the final round. Because IRV collects additional preferences beyond first, given the same number of candidates, IRV is more likely to find a majority than would be the case with a Plurality election.

However, if there are exhausted ballots, not showing a preference between the two remaining candidates, that last round majority may still only be a plurality with respect to valid ballots cast in the election.

There are two sources of this failure of incomplete ranking:

1. Some IRV implementations don't allow complete ranking, either due to voting machine limitations or other reasons; for example, in San Francisco, only three ranks are available on the ballot, whereas there may be over twenty candidates.
2. Some voters don't rank enough of the candidates to express a preference between the final two candidates, even if the ballot allows it.

In both cases such ballots, with all choices eliminated, are considered exhausted and don't count for or against any remaining candidate, in most implementations of IRV. While some critics may argue that exhausted votes may prevent a true majority winner, if this strict definition of "majority" is used as a criterion, it is note worthy that in most plurality elections at least up to the year 2009, a significant number of people eligible to vote did not show up to the polls, preventing a true "majority" winner. Incomplete ballots that are exhausted may be no worse to society than eligible voters who chose to stay home.

To avoid this issue, in Australia it is generally required that voters rank all candidates, which, by definition, creates a majority winner, because ballots not ranking all candidates are considered spoiled and invalid, but this has not been proposed for the United States. In New South Wales and Queensland, however, Optional Preferential Voting has been introduced as a reform, thus finding no absolute majority becomes, once again, possible. Antony Green notes that "The exhaustion rate has approached 80% in some seats.... In summary, optional preferential voting almost always assists the party with the highest primary vote."

Cheaper to administer than a two-round runoff

Because it does not require two separate votes, IRV can present cost savings relative to a two-round system. In some cases, a primary election can be avoided as well.

After the initial cost of equipment, IRV can reduce costs of a second election (required in a two round system or nonpartisan primary).

Eliminates the so-called "spoiler" effect

In plurality elections with three or more candidates, it is possible for every candidate to earn a minority of the vote. When that happens, the candidate or party earning the second-largest minority of the vote sometimes labels the election "spoiled", the rationale being that the votes actually earned by the third-place candidate would have been cast for the second-place candidate, if only third-party candidates were prohibited from participating in elections.

IRV eliminates the spoiler effect in many cases. Under IRV, voters are not forced into choosing between the lesser of two evils and are able to cast runoff (second-choice) votes for as many candidates as they find acceptable. During each round of IRV vote tabulating, the candidate with the least number of votes is dropped and the second-choice votes on his ballots are allocated to the remaining candidates. If need be, the process continues until there are only two candidates remaining, at which point there isn't any "spoiler" candidate for the second-place candidate to blame.

Using ranked preference ballots, more candidates can run without "spoiling" being a factor. In Australia's national elections in 2007, for example, the average number of candidates in a district was seven, and at least four candidates ran in every district. Every seat was won with a majority of the vote, including several where results would have been different under plurality voting.

In the United States, IRV addressed the spoiler effect in Ann Arbor, Michigan, where IRV was implemented in 1975 after passing in a 1974 referendum. It resulted in election of the city's first African-American mayor, a Democrat, who won after trailing the Republican incumbent 49% to 40% in the first count of ballots, with remaining votes cast for the Human Rights Party. A new referendum to rescind the reform was then placed on the ballot for a special election, with low turnout, which reversed the reform.

Other election reformers argue that there are other single-winner voting systems that could reduce or eliminate the spoiler effect to a greater degree than IRV.

Gives voters a wider range of choices

Like the two-round system, IRV tends to give voters a wider range of choice among candidates than plurality. More independent and third party candidates are likely to run because the spoiler problems are less severe. The sequential method of IRV accommodates choices differently than runoff voting by not immediately reducing the field to two in the second round, as typically done in runoff elections like the French presidential election, 2002.

May reduce negative campaigning

John Russo, Oakland City Attorney, argued in the Oakland Tribune that "Instant runoff voting is an antidote to the disease of negative campaigning, and the New York Times in a 2004 news article highlighted how some San Francisco candidates were conducting their campaigns more cooperatively. Under the system, their candidates were less likely to engage in malicious campaigning because such tactics would risk alienating the voters who support 'attacked' candidates."

However, critics allege there is a lack of evidence that such an effect occurs as often as suggested.

No formal studies are known to have been conducted in the United States. Internationally, scholarship by Benjamin Reilly suggests instant runoff voting eases ethnic conflict in divided societies, and this feature was a leading argument for why Papua New Guinea adopted instant runoff voting.

Potential disadvantages of IRV

Plurality voting is good enough

Plurality supporters point to the fact that most elections in the U.S. use plurality voting, and voters seem to accept plurality winners as legitimate, suggesting that, "If it ain't broke don't fix it." The fact that some revered leaders, such as Abraham Lincoln, did not receive a majority of the vote is sometimes mentioned.

It can be claimed that the spoiler effect is not a weakness but a strength because it encourages and rewards like-minded candidates and voters to work together before the election. This encourages the formation of strong coalitions or parties, who attempt to best represent a collective position to the largest set of voters they can. Thus once an election is held, all compromising work has been completed and it's up to the voters to decide a first choice and accept the results as best.

Writing in the Canadian Journal of Political Science, Harold J. Jansen studied the Alternative Vote in Canada, concluding that "On balance, it differed little from the single member plurality system."

May violate the one person one vote mandate

Ann Arbor, Michigan, through a petition drive, implemented "preference voting" in 1974. The arguments given in letters to newspapers included "Gives minority candidate voters two votes." In the other direction, it was argued, "The same 'two vote privilege' is extended to supporters of losing candidates in primaries or where there are run-off elections." This procedure went before the Michigan courts, and a ruling was issued in Stephenson vs. the Ann Arbor Board of City Canvassers in 1975. Majority Preferential Voting (or M.P.V., as it was called) was upheld as in compliance with the constitution. In his decision, Judge James Fleming wrote that

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.

Two years after voting to use Instant Runoff Voting to elect their Mayor, the voters of Ann Arbor voted to repeal IRV.

Increased distribution of election costs

Pierce County, Washington election officials outlined costs of $3,291,340 to implement IRV for its elections in 2008, including for new software and equipment, voter education, testing, share of time of permanent staff, consultants and additional ballot printing and postage costs. All ballots cast at the precinct had to be counted by central scanners, with requirements for more staff time to check in, visually scan and tabulate ballots. In 2009 the auditor [chief elections director of Washington counties] reported ongoing costs that are not always balanced by the costs of eliminating primaries for most county offices, as those primaries may be needed for other offices not elected by IRV.

May increase the use of computer counting equipment

Some opponents of IRV fear that its more complex ballot counting process will lead to fully computerized counting of more elections, and potentially more computer counting fraud. IRV supporters attempt to answer these claims with recommended audit procedures.

Compared to other reform alternatives

Claimed advantages

Greater track record / more politically viable

IRV has been used for national elections for several decades in such nations as Australia and the Republic of Ireland, and forms of it have been adopted for other significant public elections such as London and Wellington, New Zealand. In the United States, a number of local jurisdictions have voted to replace two-round runoff or plurality voting elections, and recent presidential candidates Barack Obama, Howard Dean, John McCain and Dennis Kucinich have taken public positions in favor of IRV. IRV also is widely used in major non-governmental elections.

Claimed disadvantages

Fails the monotonicity criterion

Like all multi-round election methods that eliminate candidates between rounds of counting, IRV fails the monotonicity criterion: a candidate should not be disadvantaged if some voters increase their support for the candidate, or conversely should not be rewarded by voters decreasing their support (when all other candidates retain their relative ordering). In IRV elections, the reallocation of ballot papers from an eliminated candidate can alter the balance of votes of the other candidates, making IRV sensitive to vote changes that alter which candidate is eliminated in a particular round.

Candidate	Round 1	Round 2	Result
Candidate A	40%	40% + 5%	—
Candidate B	31%	31% + 24%	winner
Candidate C	29%	—

Candidate	Round 1	Round 2	Result
Candidate A	37%	37% + 16%	winner
Candidate B	31%	—
Candidate C	32%	32% + 15%	—

Consider the following 3-candidate situation: candidate A wins the first round with most votes but no overall majority. The election progresses to a second round in which the votes from the eliminated candidate (C) are redistributed. Assume that the preference among these is for B over A; in other words, the majority of supporters of C gave an ordering C > B > A. In this situation, B may defeat A in the second round run-off.

Backers of candidate A can improve their chances by counterintuitively switching support to the rival candidate C (indeed, their arch-rival, given that C's supporters largely placed B second). They must be careful to do so in the correct proportion, but if they are able to push C's vote just beyond that of B (changing their ballots from A > C > B to C > A > B), they can force B's elimination at the first round. Even if we assume that B is only a "middle ground" candidate, with an equal number of supporters favouring A in second place as favour C, the redistribution of votes may allow A to clinch victory from C in the final run-off.

For tactical voters to employ this strategy in practice would require near-complete knowledge of how everyone else will vote: switching their allegiance to a rival in insufficient numbers affords no benefit to their candidate, while excessive support for their rival can eliminate their candidate prematurely. Austan-Smith and Banks argued, in 1991, that "monotonicity/nonmonotonicity in electoral systems is a nonissue." What fraction of possible (or likely) outcomes are non-monotonic under IRV is an open question.

IRV fails to challenge the lack of minority representation

IRV does not address the fact that in legislative elections, having one representative elected by majority vote may leave many voters with a "representative" they oppose. Many backers of proportional representation voting methods in Canada and the United Kingdom do not support instant runoff voting for legislative elections.

IRV fails the Condorcet criterion

IRV can eliminate, and thus fail to select as winner, a Condorcet winner, i.e. a candidate preferred by a majority to each other candidate in the field (including the eventual winner under IRV). For example, in a three-candidate field suppose that 40% of voters have the ranking XYZ, another 40% have the reverse ZYX, and the remaining 20% have Y as first preference. Here Y is eliminated in the first round of the count, despite being preferred by a (different) majority to each of X and Z. And such a scenario is not fanciful: think of a centrist party that is the first preference of fewest voters but the second preference of many more on both sides.

IRV advocates point out that the two other most commonly used methods for single winner elections (traditional runoff elections and plurality voting) are more likely than IRV to elect a non-Condorcet winner. Although there are few reported examples of IRV failing to elect the Condorcet winner in governmental elections, computer simulations show that IRV does not necessarily result in electing the Condorcet winner, and can behave erratically. Failing the Condorcet criterion, like failing the monotonicity criterion, is also related to the resistance IRV and contingent vote have against strategic and tactical voting, by eliminating the possibility of the "burying" strategy.

Global Usage

Australia

The first known use of IRV in a governmental election was in 1893 in an election for the colonial government of Queensland, in Australia. The system used for this election was a special form known as the contingent vote. IRV in its true form was first used in 1908 in a State election in Western Australia. Instant-runoff voting is used to elect members of the Australian House of Representatives.

The preferential system was introduced in 1918 after the Swan by-election, in response to the rise of the conservative Country Party, a party representing small farmers. The Country Party split the anti-Labor vote in conservative country areas, allowing Labor candidates to win on a minority vote. The conservative government of Billy Hughes introduced preferential voting as a means of allowing competition between the two conservative parties without putting seats at risk. It was first used at the Corangamite by-election on 14 December 1918. It had previously been introduced as a result of the work of Thomas Hare and Andrew Inglis Clark in the Tasmanian House of Assembly.

Preferential voting has gradually extended to both upper and lower houses, in the federal, state and territory legislatures, and is also used in municipal elections, and most other kinds of elections as well, such as internal political party elections, trade union elections, church elections, elections to company boards and elections in voluntary bodies such as football clubs. Negotiations for disposition of preference recommendations to voters are taken very seriously by candidates because transferred preferences carry the same weight as primary votes.

Canada

IRV was used in 2009 to elect the leader of the Liberal Party of Canada in a national primary and in 2004 was used to select Stephen Harper as leader of the Conservative Party of Canada. It is also used to elect the Canadian Wheat Board.

From 1927 to 1956, the Province of Manitoba used instant-runoff voting in rural and suburban districts outside of Winnipeg (which itself used the single transferable vote in multi-member electoral districts).

Ireland

IRV is used to elect the President of Ireland.

Papua New Guinea and Fiji

Instant runoff voting is use to elect the national parliament of Papua New Guinea, and the Fijian House of Representatives.

New Zealand

IRV is used to elect some mayors in New Zealand, including in Wellington.

United Kingdom

IRV, known as Alternative Vote, is used to elect the leaders of the Labour Party and the Liberal Democrats in the United Kingdom. The supplementary vote form of instant runoff voting is used to elect the mayor of London and other cities in the United Kingdom. In September 2009, British Prime Minister Gordon Brown's commitment that his party would hold a national referendum on adoption of instant runoff voting for elections of House of Commons drew public support. In February 2010, he announced that a referendum on changing the longstanding Westminster voting system could be held by the "end of October 2011" if the idea was approved by MPs. On 9 February 2010, MPs supported by 365 votes to 187 an amendment to the Constitutional Reform and Governance Bill that would see the referendum held by October 2011. However, as a general election was called for 6 May 2010, this part of the bill was lost during the wash-up period prior to the dissolution of Parliament. However, after the May 2010 elections, the new coalition government of the Conservative and Liberal Democrat parties announced its support for a national referendum.

United States

Further information: IRV implementations in United States

Since 2002, instant runoff voting has been adopted in several cities in the United States. As of February 2010, 79 elections have been held in eight counties, cities or towns: San Francisco, California; Burlington, Vermont; Takoma Park, Maryland; Cary, North Carolina; Hendersonville, North Carolina; Aspen, Colorado; Minneapolis, Minnesota; and Pierce County, Washington.

Several other cities have approved it, but have not yet implemented it. Among them are the California cities of Berkeley, Oakland and San Leandro, where IRV will be used in city elections for the first time in November 2010. Saint Paul, Minnesota, is scheduled to use IRV for first time in 2011 for city council elections, and Memphis, Tennessee, to use IRV in its 2011 council elections.

Not all jurisdictions have kept using IRV. Pierce County, Washington, repealed IRV by referendum in November 2009, and Burlington, Vermont repealed IRV in March 2010. The city council in Cary, North Carolina, voted to participate in an IRV pilot program in 2007, but did not do so in 2009. In 2009, voters in Aspen, Colorado, narrowly rejected an advisory measure on whether to keep IRV, and its city council may place a binding vote on the ballot. In 1976 IRV was repealed after one election in Ann Arbor, Michigan.

IRV has survived at least three legal challenges in the United States. A case brought against IRV in Minneapolis went to the Minnesota Supreme Court, which in June 2009 unanimously upheld the system. A 1975 lawsuit brought against IRV in Ann Arbor, Michigan, also was rejected. In April 2010, a federal judge rejected a lawsuit claiming that San Francisco's current method of implementing IRV is unconstitutional.

Non-governmental organizations

The sequential elimination method used by IRV is described in Robert's Rules of Order Newly Revised, 10th edition. as an example of "preferential voting," a term covering "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 ... by way of illustration." And then the instant runoff voting method is 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 less widely-used 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.

Forms of instant runoff voting have been adopted by various private and non-profit associations, particularly in the United States, Australia, the United Kingdom and Canada. In August 2009, the Academy of Motion Pictures announced that its best picture "Oscar" will be elected by instant runoff voting in 2010. The Producers Guild of America in September 2009 announced that it also would use IRV to select its best film award. Other examples in the United States include the 160,000-member American Chemical Society, 150,000-member American Psychological Association, 38,000-member American Psychiatric Association,100,000-member American Association of University Women and 56,000 member American Mensa. The American Political Science Association has long had the "alternative vote" in its constitution for electing its national President-Elect by mail under certain conditions, although there has not been a contested election for APSA President since about 1970. Updated in March 2009, a list of organizations with links to their bylaws is available at the advocacy organization FairVote.

As of April 2010, at least 56 American college and university student governments have either adopted and actively use IRV, or approve and provide for its use in internal elections. A list of such colleges and universities and examples of their contested elections with IRV is available at the advocacy organization FairVote.

Similar systems

Runoff voting

The term instant runoff voting is derived from the name of a class of voting systems 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. The simplest form of runoff voting is the two round system. Under the two round system voters vote for only one candidate but, if no candidate receives an overall majority of votes, another round of voting is held from which all but the two candidates with most votes are excluded.

Exhaustive ballot

A closer system to IRV is the exhaustive ballot. In this system—one familiar to fans of the television show American Idol – only 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. Instant runoff voting is so named because it achieves a similar effect to runoff voting but it is necessary for voters to vote only once. The result can be found 'instantly' rather than after several separate votes.

Two round systems

Runoff voting differs from IRV in a number of ways. The two round system can produce different results due to the fact that it uses a different rule for eliminations, excluding typically all but two candidates after just one round, rather than gradually eliminating candidates over a series of rounds. However all forms of "delayed" runoff voting differ from IRV in that voters can change their preferences as they go along, using the results of each 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.

Contingent vote

Top-two IRV

The contingent vote, also known as Top-two IRV, or batch-style, is the same as IRV except that all but the two candidates with most votes are eliminated after the first round; the count therefore only ever has two rounds. This differs from the 'two round' runoff voting system described above in that only one round of voting is conducted. The two rounds are only for counting and both take place after voting has finished. Two particular variants of the contingent vote differ from IRV in a further way. Under the forms of the contingent vote used in Sri Lanka, and the elections for Mayor of London in the United Kingdom, voters are not permitted to rank all of the candidates, but only a certain maximum number. Under the variant used in London, called the supplementary vote, voters are only permitted to express a first and a second preference. Under the Sri Lankan form of the contingent vote voters are only permitted to rank three candidates. The supplementary vote is used for mayoral elections while the Sri Lankan contingent vote is used to elect the President of Sri Lanka.

While superficially similar to "sequential elimination" forms of IRV, these contingent vote forms of IRV can produce different results. If, as occurs under all forms of the contingent vote, more than one candidate is excluded after the first count, a candidate might be eliminated who would have gone on to win the election under sequential elimination IRV. If voters are restricted to a maximum number of preferences then it is easier for their vote to become exhausted. This encourages voters to vote tactically, by giving at least one of their limited preferences to a candidate who is likely to win.

Conversely, a practical benefit of the 'contingent vote' counting process is expediency and confidence in the result with only two rounds. Most apparent in smaller elections, like with fewer than 100 ballots among a dozen choices, confidence can be lost in a bottom-up elimination due to cumbersome ties on the bottom (or near ties affected by counting errors). Frequent and even multiple use of tie-breaking rules in one election will leave uncomfortable doubts over whether the winner might have changed if a recount was performed.

IRV in a larger runoff process

IRV may also be used within a part of a larger runoff process:

• In some jurisdictions where top two runoff is required if no candidate gets a majority, a provision has been implemented that allows absentee voters to cast a ranked ballot. In the short window between the first election and the runoff, there often is not enough time to deal with absentee voters. With a ranked ballot, the votes of overseas citizens can count even if their first choice does not make the runoff. Arkansas, Louisiana, South Carolina and Springfield (IL) all have implemented this form of instant runoff voting on ballots for military and overseas voters.
• It can be used to automate a faster runoff elimination of weak candidates in early rounds of an exhaustive ballot runoff, with specific rules defined that can stop with process with two or more candidates remaining for further balloting.
• It can support a higher winner threshold not guaranteed by a single balloting, (like 60%). In such cases a second balloting may be used to confirm the winner.
• Elections requiring a majority winner defined by the total number of ballots may not be achieved with a single IRV balloting due to exhausted ballots. In such cases a post-balloting process may be needed to determine a final winner.
• Roberts Rules of Order, Newly Revised recommends preferential voting for elections by mail, giving the STV technique used by IRV as their example; however, the RRONR version still suggests a majority of votes cast to elect a winner. For in-person elections, they recommend repeated balloting until a candidate wins with an absolute majority of all voters. Repeated ballot allows voters in a new election to turn to a candidate as a compromise who may not have polled well in the initial election.

The term "instant runoff voting" is often applied to all these variations, with the common feature being one-vote counted per ballot at a time, with rules defined to eliminate one or more candidates each round with the fewest votes and transfer uncovered votes for remaining candidates; however, the term implies replacement of runoff elections, and most IRV implementations do accordingly drop the majority election requirement.

Theoretical evaluation by voting system criteria

Main article: Voting system § Criteria in evaluating single winner voting systems

Scholars of electoral systems often compare them using mathematically-defined voting system criteria, the value of some of which is controversial. Some of the criteria are considered by Arrow's Theorem and the Gibbard-Satterthwaite theorem, which assume that voters rank all candidates in a strict preference order, among other assumptions that do not hold for all methods. For methods, such as IRV, which use such ranked preferences, satisfying all of the criteria is impossible, because they are mutually exclusive.

• IRV passes the majority criterion, the later-no-harm criterion, the mutual majority criterion, the resolvability criterion, the Condorcet loser criterion, and, if the right tie-breaker method is used, the independence of clones criterion.
• IRV fails the monotonicity criterion, consistency criterion, the Condorcet criterion, the participation criterion, reversal symmetry, and the independence of irrelevant alternatives criterion.

See also

• Alternative Vote Top-up, or Alternative Vote Plus (AV+) proposed by the Jenkins Commission (UK)
• Australian electoral system
• Ballot Access News for occasional related news in the United States
• Electoral systems of the Australian states and territories
• List of democracy and elections-related topics
• None of the above (NOTA) or Re-Open Nominations (RON)
• Preferential block voting – An instant runoff process for electing multiple seat elections.
• Table of voting systems by country
• Single transferable vote

External links

IRV in practice

• Advantages and disadvantages of AV from the ACE Project Electoral Design Reference Materials
• A Handbook of Electoral System Design from International IDEA
• Australian Electoral Commission Web Site
• Preferential Voting in Australia from Australian Politics.com
• San Francisco Department of Elections, California
• Alameda County Registrar of Voters, California
• City of Minneapolis, Minnesota

Demos and simulations

• Indaba.org – Demo of an IRV Ballot, including the Visual Display of a Runoff
• BBC: Would the alternative vote have changed history?, illustration of how the results of the last six general elections might have looked had the 'alternative vote' system been in place.
• OpenSTV – Open source software for computing IRV and STV
• Favourite Futurama Character Poll
• Voting System Visualizations – 2-dimensional plots of results of various systems.
• Simulation Of Various Voting Models for Close Elections Opposition article by Brian Olson.

Advocacy organizations

• Instant Runoff Voting at FairVote
  • History of IRV
• League of Women Voters of Vermont
• InstantRunoff.com
• Roosevelt Institution
• Citizens for Voter Choice :: Massachusetts
• Common Cause Massachusetts

Opposition positions

• IRV page at the Center for Range Voting
• Instant Runoff Voting Report Values and Risks Report by the N.C. Coalition for Verified Voting
• Voting methods: tutorial and essays by James Green-Armytage (for IRV, see e.g. 1 2 3 4 5)