Single transferable vote
Single transferable vote (STV) is a type of multi-winner ranked-choice voting method; an electoral system in which voter may rank the candidates according to their preferences, so their single vote can be transferred to other candidates (if needed) based on these rankings to avoid votes being wasted. STV aims to provide proportional representation for every constituency, meaning each vote is effectively worth about the same, unlike majoritarian systems, no one party or voting bloc can take all the seats in a district. Under STV, each voter casts a single, ranked-choice vote and the system  selects multiple winners for a constituency (a multi-member district). Every sizeable group within the district wins at least one seat: the more seats the district has, the smaller the size of the group needed to elect a member and the ranked voting allows voter to form consensus behind the most-popular candidates. The main characteristics of STV are the following: How STV works. Each voter not only marks their most preferred candidate on the ballot, but also their other preferences. A vote goes to the voter's first preference if possible, but if the first preference is eliminated, instead  of being thrown away, the vote is transferred to the next available preference based on the ranked-choice ballot. This means, instead of the vote being wasted, it is assigned to the voter's second, third, or lower choice if possible or, under some systems, it is apportioned fractionally to different candidates. As long as there are more candidates than seats, the least popular candidate is eliminated and votes they received are transferred based on their voters' subsequent preferences. Before the election, a quota (the minimum number of votes that guarantees election) is calculated and candidates who accumulate that number  of votes are declared elected. In most systems, this is also used to determine surplus votes (votes not needed by successful candidates to win, i.e. votes over the quota). Elections, eliminations and vote transfers continue until enough candidates are declared elected (all seats are filled by candidates reaching the quota) or until there are only as many remaining candidates as there are unfilled seats, at which point the remaining candidates are declared elected. The specific method of transferring votes varies in different systems (see ). District elections grow more proportionally representative in direct relation to increase in the number of seats  to be elected in a constituencythe more seats, the more the distribution of the seats in a district will be proportional. For example, in a three-seat STV election using the Hare Quota of formula_1, a candidate or party with 33 percent of the votes is guaranteed to win a seat. In a seven-seat STV district, any candidate who can get the support of approximately 14 percent of the vote (either first preferences alone or a combination of first preferences and lower-ranked preferences transferred from other candidates) will win a seat. Because of this quota-based fairness, it  is extremely rare for a party to take a majority of the seats in a district without a majority of the vote. Additionally, a majority of voters see their vote used to elect the candidates who make up a majority of the district's elected members. Example for a non-partisan election. Suppose an election is conducted to determine what three foods to serve at a party. There are 5 choices - Oranges, Pears, Chocolate, Strawberries, and Hamburgers. Only three of them will be served. The hope is that each guest will be served at least one food that they are  happy with. It is decided to use STV to make the decision so each guest is given one vote and also allowed to cast one back-up preference to be used only if the first preference can not elect a food or to direct transfer of surplus votes if it does. The 23 guests at the party mark their ballots according to the table below, with first and second preferences marked by each voter. First, the quota is calculated. Using the Droop quota, with 23 voters and 3 winners to be found, the number of votes required to be elected  is: When ballots are counted the election proceeds as follows: Result: The winners are Chocolate, Oranges and Strawberries. This result differs from the one that would have occurred if the three winners were decided by first preference plurality rankings, in which case Pear would have been a winner, as opposed to Strawberry, for having a greater number of first preference votes. If the voters had been able to choose only one food to serve (as in first-past-the-post, it is likely that Chocolate, the choice of only slightly more than half of the 23 party-goers, would have  won and Chocolate would be the only food served at the party. STV in this case produced a high level of effective votesvotes used to elect the successful candidates. 18 voters saw their first preference elected, and three more saw their second preference elected. Only two, those who voted for hamburgers with pears as their second preference, did not see any of their choices elected. Example for an election with parties. There are 5 seats in a district. Party A runs 5 candidates and Party B runs 3, there is also one independent in the race. The election is conducted  under STV with the Hare quota, which for five candidates is at 20% (100% divided by five). First round. In the first round, the very popular candidate of Party A, Candidate A3 is above the quota, so they win a seat. Surplus votes are distributed, the voters of Candidate A3 have put another politician from their party, Candidate A4 as their second preference, so they now get these 5% of votes. Second and third rounds. In the second and third rounds the least popular candidates are eliminated (Candidates A1 and A5) and their votes transferred to their next preferences. Voters  of Candidate A5 are not very partisan, they actually prefer the independent candidate over the other candidates of Party A still in the race. Forth round. In the next round, Candidate A2 is eliminated with all their votes going to the candidate A4, the last remaining candidate from Party A, who gets elected. All these voters who helped elect Candidate A4 prefer the independent candidate to the candidates of the other party so their vote will go to Fifth round. Finally Candidate B1 is also eliminated. There are now only 3 candidates in the race, so they automatically get the  remaining seats regardless of whether they reached the quota. Compared to other systems. Under STV candidates A3, A4, I, B2 and B3 got elected. This is different than if all voters could only vote for their first preference, which is called the single non-transferable vote. In this case the seemingly most popular five candidates would have been elected, which were candidates A3, B2, B3, B1 and A2, meaning even though Party B-s candidates had less support together, have got 60% of seats, and the Party A only 40%. In this case, Party A overextended themselves by fielding too  many candidates, but even if they strategical nominated only 3, there would not necessarily have been successful in gaining a seat, unless their voters used coordinated strategic voting. If all voters could vote for 5 candidates (but not ranked), which is called block voting, a type of multiple non-transferable vote, Party A could have won all seats leaving Party B and voters of the independent candidate without representation. This is because if all voters of Party A voted for all 5 of their candidates, every Party A candidate could have received up to 48% of the votes, and some  even up to 55% if voters of Candidate I also voted for some Party A candidates with their 4 other votes. At the same time, all of Party B's candidates could only get up to 45% or at best 52% with the same tactics. If the voters are partisan enough, the likely outcome is that one party can take all the seats (majoritarian representation) and all other votes are wasted. STV meanwhile is roughly proportional (as much as the number of seats allows) and takes into account not just the first preferences of voters. In the example it could  be seem that even some voters, who might like a candidate from a certain party best, might prefer and independent (or even a rival party candidate) before other candidates of that party. This means that even if it seems that some faction (based on first preferences) is overrepresented or underrepresented in the outcome, this could also be the outcome that follows from the voters alternative preferences. Related voting systems. Instant-runoff voting (IRV) is the single-winner analogue of STV. It is also called "single-winner ranked-choice voting". Its goal is representation of a majority of the voters in  a district by a single official, as opposed to STV's goals of not only the representation of a majority of voters through the election of multiple officials but also of proportional representation of all the substantial voting blocks in the district. Single non-transferable vote (SNTV) produces much the same representation as STV, without the work and complication of vote transfers. Single voting in a multiple-member district produces mixed roughly proportional representation, which STV's vote transfers sometimes does not alter. (An example is the election of Edmonton, Alberta, MLAs through STV in 1930. The winners were the  same under STV as would have been elected under SNTV.) Indirect single transferable voting is a non-ranked-vote version of STV. Single voting in a multi-seat district is retained. Voters do not mark their ballots with rankings, but votes are transferred, as needed, based on the eliminated or elected candidate's pre-set instructions. This is a useful system to achieve many of the benefits of STV in districts where it is difficult to collect all the ballots in one central place to conduct STV transfers or where X voting is preferred over ranked voting due to voters ' inability or disinterest in ranking candidates. Once known as the Gove system, or the schedule system of PR, it was invented by Massachusetts legislator William H. Gove of Salem and Archibald E. Dobbs of Ireland, author of "Representative Reform for Ireland" (1879). Terminology. When single transferable voting is used for single-winner elections, it produces a system that is formally called instant-runoff voting. STV uses preferential votes cast in multi-seat districts, but some use the term "preferential voting" when they are talking only about instant-runoff voting. "Preferential voting" can also refer to a broader category, ranked voting  systems. In the United States, STV is sometimes also called preferential voting, choice voting or preference voting. STV used for multi-winner elections is sometimes called "proportional representation through the single transferable vote", or PR-STV or STV-PR (in Scotland). "STV" usually refers to the multi-winner version, as it does in this article. Hare–Clark is the name given to PR-STV elections in Tasmania and the Australian Capital Territory. Balloting. In STV, each voter casts just one vote although multiple seats are to be filled in the district. They can provide alternate preferences to be used if  needed by ranking the candidates in order of preference. In practice, the candidates' names are usually organized in columns so that voters are informed of the candidates' party affiliations or whether they are standing as independents. An alternative way to mark preferences for candidates is to use columns for the voters' preference. One column shows first preference. An X there goes beside the most-preferred candidate. The next column is for the second preference. An X there marks the second-preference candidate, etc. Filling seats under STV. The use of quota to fill seats. In most STV elections, a quota  is established to ensure that all elected candidates are elected with approximately equal numbers of votes. In some STV varieties, votes are totalled, and a quota (the minimum number of votes that guarantees election) is derived. Another system, which used four-seat districts, set quota at 25 percent of the votes in a district. Once a quota is determined, candidates' vote tallies are consulted. If a candidate achieves the quota, they are declared elected. Then in some STV systems, any surplus vote is transferred to other candidates in proportion to the next highest preference marked on the ballots received by  that candidate. If more candidates than seats remain, the candidate with the fewest votes is eliminated, with their votes being transferred to other candidates as determined by the voters' next preference. Elections and eliminations, and vote transfers where applicable, continue until enough candidates are declared elected to fill the open seats or until there are only as many remaining candidates as there are unfilled seats, at which point the remaining candidates are declared elected. These last candidates may be elected without surpassing quota, but their survival until the end is taken as proof of their general acceptability by the voters . Finding winners using quota. An STV election count starts with a count of each voter's first choice, recording how many for each candidate, calculation of the total number of votes and the quota and then taking the following steps: There are variations in conducting transfers (see ). When the number of votes transferred from the losing candidate with the fewest votes is too small to change the ordering of remaining candidates, no transfer is made or more than one candidate is eliminated simultaneously. Vote transfers and quota. STV systems primarily differ in how they transfer surplus votes and in the  size of the quota. For this reason some have suggested that STV can be considered a family of voting systems rather than a single system. The quota, if used, must be set at a level where no more candidates can reach quota than there are seats to be filled. The quota is the minimum number of votes that ensures a candidate is elected. Any candidate that takes the quota is declared elected. It cannot be so small that more candidates can be elected than the number of open seats, but the smaller it is, the more fair is the  result. If fair results are to be produced and the number of candidates are pre-set, a quota must be set whereby any candidate that receives it is declared elected. There are different quotas to choose from. The Droop quota is the most commonly used quota. It is generally considered to be the absolute lowest number that elects the correct number of candidates to fill the available seats, at least based on the original number of votes cast. The Droop quota is given by the floor function formula: The Droop quota is an extension of the majoritarian principle of requiring  a 50% + 1 majority in single-winner elections under instant-runoff voting. Using Droop means 25% plus 1 is the quota in a three-seat contest because no more than three people can each have 25% of the vote + 1; using Droop means 10% of the vote + 1 is the quota in a nine-seat district because no more than nine people can each have 10% of the vote + 1, and so on. Droop being relatively low means that the largest party, if it has majority of votes, is likely to take the majority of the  seats in a district. The Hare quota was used in the original proposals by Thomas Hare. It is larger than the Droop and sometimes ensures greater representation to less-popular parties within a district. But also, being larger than Droop, Hare presents more of an obstacle to small parties who hope to take just one seat. Being smaller than Hare, the Droop quota may give a seat to a small party that does not have the votes to take a seat under Hare. There are variations in the conduct of transfers in different variations of STV, such as how to  transfer surplus votes from winning candidates and whether to transfer votes to already-elected candidates. Under STV, votes cast for losing candidates and surplus votes cast for winning candidates are sometimes transferred to voters' next choice candidates. In these ways, STV minimizes wasted votes. It can happen that a vote is set to be transferred but cannot be because it bears no subsequent preference for any remaining candidate. In the case of transfers of surplus votes, if the number of transferable votes is less than the number of the surplus, no math is needed to make the transfer. Transfer  of the transferable votes is done simply by reference to subsequent preference on the votes. If the variation of STV used allows transfers to candidates already elected, when a candidate is eliminated and the next preference on the ballot shows preference for a candidate already elected, votes are transferred to already victorious candidate. The new surplus votes for the victorious candidate (transferred from the eliminated candidate) are then transferred to the next preference of the victorious candidate, as happened with their initial surplus. However, any vote transfers from the victorious candidate to a candidate who was already eliminated are impossible , and reference must be made to the next marked preference, if any. See for details. A quota set lower than Droop is sometimes workable. If fractional votes are used in an STV method, the Droop quota may be modified so that the fraction is not rounded down. Frank Britton, of the Election Ballot Services at the Electoral Reform Society, observed that the final plus one of the Droop quota is not needed; the exact quota is then simply formula_4. Without fractional votes, the equivalent integer quota may be written: So, the quota for one seat is 50 of 100 votes , not 51. In any case, in most STV elections the appearance of non-transferable votes means that the quota could be lowered significantly during the counting of the vote with no danger of having too many elected. In STV, vote transfers are of two typestransfers of votes of eliminated candidates and transfers of surplus votes of elected candidates. The first type happens more often than the second type. Surplus votes are transferred only after a candidate is elected and then only if there are still open seats to be filled and if the transfers may affect the ranking of the  remaining candidates. Transfers of votes of eliminated candidates. Transfers of votes of eliminated candidates is done simply, without the use of complex math. The next usable preference on the vote gives the destination for the transfer of the vote. If there is no usable preference on the ballot, the vote goes to the "exhausted" or non-transferable pile. Transfers of surplus votes. The transfer of surplus votes of an elected candidate may be very simply done or may be done more or less intricately, depending on the circumstances and the choice of the government or election officials. It can happen  that a vote is set to be transferred but cannot be because it bears no subsequent preference for any remaining candidate. In transfers of surplus votes, any non-transferable votes are left with the elected candidate. If the number of transferable votes is less than the surplus, the transfer of surplus votes can be performed just as it is done in the case of transfer of eliminated candidates, the only difference being that non-transferable votes remain with the elected candidate. They do not go to the exhausted pile. Transfer of the transferable votes is done in these cases  simply by reference to the next usable preference on the vote. In cases where the number of transferable votes is more than the surplus, a more-involved method is needed in order to make the transfer proportional and to ensure that the quota left with the successful candidate is proportional as well. But election officials here have a choice of using a simpler method or more involved methods. The basic formula for how to transfer surplus votes when there are more transferable votes than the surplus to be transferred is: <div> This can produce fractional votes, which are  handled differently under different counting methods. As well, not considering later preferences when transferring votes may influence later transfers and are thought of as being random, so instead some places use systems that break down the elected candidate's votes into many separate piles looking at all the permutation of preferences marked on the votes. In some STV variants, such as those used in the Republic of Ireland (except Senate elections), Malta, and elsewhere, merely the next preference is examined. Votes are transferred as whole votes. Any randomness may arise from the later preferences, if any, that may have to  be used later. But choosing the votes at random from the pile means that each transfer should be mixed and likely closely resembles the composition of the entire pile. The Gregory method (also known as Newland–Britain or Senatorial rules) eliminates randomness by examining all the preferences marked on ballots, the later preferences dictate how later transfers, if any, will go. They transfer votes as fractions of votes. Gregory is in use in Northern Ireland, the Republic of Ireland (Senate elections) and in Australia. Both Gregory and earlier methods have the problem that in some circumstances they do not treat  all votes equally. For this reason Meek's method, Warren's method and the Wright system have been invented. While easier methods can usually be counted by hand, except in a very small election Meek and Warren require counting to be conducted by computer. The Wright system is a refinement of the Australian Senate system replacing the process of distribution and segmentation of preferences by a reiterative counting process where the count is reset and restarted on every exclusion. Meek is used in local body elections in New Zealand. Meek in 1969 was the first to realize that computers make  it possible to count votes in way that is conceptually simpler and closer to the original concept of STV. One advantage of Meek's method is that the quota is adjusted at each stage of counting when the number of votes decreases because some become non-transferable. Meek also considered a variant on his system which allows for equal preferences to be expressed. This has subsequently (since 1998) been used by the John Muir Trust for electing its trustees. History. Origin. In 1896, Andrew Inglis Clark was successful in persuading the Tasmanian House of Assembly to be the first parliament  in the world elected by what became known as the "Hare-Clark electoral system", named after himself and Thomas Hare. H. G. Wells was a strong advocate, calling it "Proportional Representation". The HG Wells formula for scientific voting, repeated, over many years, in his PR writings, to avoid misunderstanding, is Proportional Representation by the single transferable vote in large constituencies. STV in large constituencies and multiple-member districts permits an approach to the Hare-Mill-Wells ideal of mirror representation. The UK National Health Service used to elect, through the first-past-the-post system in local or regional elections , only white male general practitioners to the General Medical Council. In 1979, the UK National Health Service used STV to proportionally elect women and immigrant GPs, and specialists, to the General Medical Council. Australia. Tasmania first used STV for election of members of the Tasmanian House of Assembly from 1896 to 1902. In 1909, it began to be used on a permanent basis for Assembly elections. (Instant-runoff voting was used for elections to the Tasmania Legislative Council (its upper house), with some of the members elected through STV prior to 1946.) In 1948, single transferable vote proportional representation on  a state-by-state basis became the method for electing Senators to the Australian Senate. This change has led to the rise of a number of minor parties such as the Democratic Labor Party, Australian Democrats and Australian Greens who have taken advantage of this system to achieve parliamentary representation and the balance of power. From the 1984 election, group ticket voting was introduced to reduce a high rate of informal voting but in 2016, group tickets were abolished to avoid undue influence of preference deals amongst parties that were seen as distorting election results and a form of optional  preferential voting was introduced. Beginning in the 1970s, Australian states began to reform their upper houses to introduce proportional representation in line with the Federal Senate. The first was the South Australian Legislative Council in 1973, which initially used a party list system (replaced with STV in 1982), followed by the single transferable vote being introduced for the New South Wales Legislative Council in 1978, the Western Australian Legislative Council in 1987 and the Victorian Legislative Council in 2003. The single transferable vote was also introduced for the elections to the Australian Capital Territory Legislative Assembly after a 1992 referendum . The term "STV" in Australia refers to the Senate electoral system, a variant of "Hare-Clark" characterized by the "above the line" group voting ticket, a party list option. It is used in the Australian upper house, the Senate, most state upper houses, the Tasmanian lower house and the Capital Territory assembly. There is a compulsory number of preferences for a vote for candidates (below-the-line) to be valid: for the Senate a minimum of 90% of candidates must be scored, in 2013 in New South Wales that meant writing 99 preferences on the ballot. Therefore, 95% and more  of voters use the above-the-line option, making the system, in all but name, a party list system. Parties determine the order in which candidates are elected and also control transfers to other lists and this has led to anomalies: preference deals between parties, and "micro parties" which rely entirely on these deals. Additionally, independent candidates are unelectable unless they form, or join, a group above-the-line. Concerning the development of STV in Australia researchers have observed: "... we see real evidence of the extent to which Australian politicians, particularly at national levels, are prone to fiddle with the  electoral system". As a result of a parliamentary commission investigating the 2013 election, from 2016 the system has been considerably reformed (see 2016 Australian federal election), with group voting tickets (GVTs) abolished and voters no longer required to fill all boxes. Canada. In British Columbia, Canada, a type of STV called BC-STV was recommended for provincial elections by the British Columbia Citizens' Assembly on Electoral Reform in 2004. In a 2005 provincial referendum, it received 57.69 percent support and passed in 77 of 79 electoral districts. It was not adopted, however, because it fell short of the 60 percent  threshold requirement the BC Liberal government had set for the referendum to be binding. In a second referendum, on 12 May 2009, BC-STV was defeated 60.91 percent to 39.09 percent. STV has been used in several Canadian jurisdictions. The cities of Edmonton and Calgary elected their MLAs through STV from 1924 to 1956, when the Alberta provincial government changed those elections to use the first-past-the-post system. The city of Winnipeg elected its MLAs through STV from 1920 to 1955, when the Manitoba provincial government changed those elections to use first-past-the-post. Less well known  is STV use at the municipal level in western Canada. Calgary and Winnipeg used STV for more than 50 years before city elections were changed to use the first-past-the-post system. Nineteen other municipalities, including the capital cities of the four western provinces, also used STV For elections in about 100 elections during the 1918 to 1931 period. United States. In the United States, the Proportional Representation League was founded in 1893 to promote STV, and their efforts resulted in its adoption by many city councils in the first half of the 20th century. More than twenty cities  have used STV, including Cleveland, Cincinnati and New York City. As of January 2010, it is used to elect the city council and school committee in Cambridge, Massachusetts, the park board in Minneapolis, Minnesota, and the board of assessors in Arden, Delaware. STV has also been adopted for student government elections at several American universities, including Carnegie Mellon, MIT, Oberlin, Reed, UC Berkeley, UC Davis, Vassar, UCLA, Whitman, and UT Austin. The Fair Representation Act, introduced in Congress in June 2017, would establish STV for US House elections starting in 2022. List of places using STV. STV has had its  widest adoption in the English-speaking world. The table below lists countries that use a proportional electoral system to fill a nationally elected legislative body. Detailed information on electoral systems applying to the first chamber of the legislature is maintained by the ACE Electoral Knowledge Network. Countries using PR as part of a parallel voting (mixed-member majoritarian) system are not included. Benefits and drawbacks. Benefits. Advocates for STV argue it is an improvement over winner-take-all non-proportional voting systems such as first-past-the-post, where vote splits commonly result in a majority of voters electing no  one and the successful candidate having support from just a minority of the district voters. STV prevents in most cases one party taking all the seats and in its thinning out of the candidates in the field prevents the election of an extreme candidate or party if it does not have enough overall general appeal. STV is the system of choice of the Proportional Representation Society of Australia (which calls it quota-preferential proportional representation), the Electoral Reform Society in the United Kingdom and FairVote in the USA (which refers to STV as fair representation voting and instant-runoff voting  as "ranked-choice voting", although there are other preferential voting methods that use ranked-choice ballots). Drawbacks. Critics contend that some voters find the mechanisms behind STV difficult to understand, but this does not make it more difficult for voters to rank the list of candidates in order of preference on an STV ballot paper (see ). Issues. Degree of proportionality. The degree of proportionality of STV election results depends directly on the district magnitude (i.e. the number of seats in each district). While Ireland originally had a median district magnitude of five (ranging from three to nine) in 1923, successive  governments lowered this. Systematically lowering the number of representatives from a given district directly benefits larger parties at the expense of smaller ones. Supposing that the Droop quota is used: in a nine-seat district, the quota or threshold is 10% (plus one vote); in a three-seat district, it would be 25% (plus one vote). A parliamentary committee in 2010 discussed the "increasing trend towards the creation of three-seat constituencies in Ireland" and recommended not less than four-seaters, except where the geographic size of such a constituency would be disproportionately large. STV provides proportionality by transferring votes  to minimize waste, and therefore also minimizes the number of unrepresented or disenfranchised voters. Difficulty of implementation. A frequent concern about STV is its complexity compared with single-mark voting methods, such as plurality voting or party-list proportional representation. Before the advent of computers, this complexity made ballot-counting more difficult than for some other voting methods. The algorithm is complicated. In large elections with many candidates, a computer may be required. (This is because after several rounds of counting, there may be many different categories of previously transferred votes, each with a different permutation of early preferences and  thus each with a different carried-forward weighting, all of which have to be kept track of.) Role of political parties. STV differs from other proportional representation systems in that candidates of one party can be elected on transfers from voters for other parties. Hence, STV may reduce the role of political parties in the electoral process and corresponding partisanship in the resulting government. A district only needs to have four members to be proportional for the major parties, but may under-represent smaller parties, even though they may well be more likely to be elected under STV than under  first-past-the-post. By-elections. As STV is a multi-member system, filling vacancies between elections can be problematic, and a variety of methods have been devised: Tactics. If there are not enough candidates to represent one of the priorities the electorate vote for (such as a party), all of them may be elected in the early stages, with votes being transferred to candidates with other views. On the other hand, putting up too many candidates might result in first preference votes being spread too thinly among them, and consequently several potential winners with broad second-preference appeal may  be eliminated before others are elected and their second-preference votes distributed. In practice, the majority of voters express preference for candidates from the same party in order, which minimizes the impact of this potential effect of STV. The outcome of voting under STV is proportional within a single election to the collective preference of voters, assuming voters have ranked their real preferences and vote along strict party lines (assuming parties and no individual independents participate in the election). However, due to other voting mechanisms usually used in conjunction with STV, such as a district or constituency system, an election  using STV may not guarantee proportionality across all districts put together. A number of methods of tactical or strategic voting exist that can be used in STV elections, but much less so than with first-past-the-post elections. (In STV elections, most constituencies will be marginal, at least with regard to the allocation of a final seat.) Elector confusion. STV systems vary, both in ballot design and in whether or not voters are obliged to provide a full list of preferences. In jurisdictions such as Malta, Republic of Ireland and Northern Ireland, voters may rank as many or as  few candidates as they wish. Consequently, voters sometimes, for example, rank only the candidates of a single party, or of their most preferred parties. A minority of voters, especially if they do not fully understand the system, may even "bullet vote", only expressing a first preference, or indicate a first preference for multiple candidates, especially when both STV and plurality are being used in concurrent elections. 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 transferred and therefore loses an opportunity to influence the result. However the number found to be non-transferable under STV is less than are ignored or wasted under the first-past-the-post system. Some votes found to be non-transferable are that way because the choices marked have already been elected, so the voter may be pleased with the overall election result even though their first preference was not elected and their vote itself was not used to elect anyone. Even if a voter marks many alternate  preferences, the vote will still be found to be non-transferable, if at any point the vote needs to be transferred and all the preferences listed next have already been eliminated or elected. But the number of non-transferable votes is fewer than the number of ignored votes under first-past-the-post and the number of effective votes, votes actually used to elect someone, is higher than under all but the most landslide first-past-the-post election contests. The STV method can be confusing, and may cause some people to vote incorrectly with respect to their actual preferences . STV ballots can also be long; having multiple pages increases the chances of people not marking multiple preferences and thus missing later opportunities to have their vote transferred. However, after a vote has been transferred a couple times and it now is at the end of the count and just three candidates remain in the running for the last seat, the voter may have little interest in the choice. None of them were the voter's first choice, nor their second or third preference. And perhaps the voter has already seen one or two of their earlier choices already elected . Many votes up for transfer are found to be non-transferable in the last vote transfers. Some at the end are elected with partial quotas, due to the number of non-transferable votes. But in STV elections a majority of votes are used to elect the members who are elected. Other. Some opponents argue that larger, multi-seat districts would require more campaign funds to reach the voters. Proponents argue that STV can lower campaign costs because like-minded candidates can share some expenses. Proponents reason that negative advertising is disincentivized in such a system, as its effect is diluted  among a larger pool of candidates. In addition, candidates do not have to secure the support of at least 50% of voters, allowing candidates to focus campaign spending primarily on supportive voters. As well, under STV, it is not necessary to be the most popular candidate in the district to be elected; it is only necessary to have quota (or survive to the end when the remaining candidates are declared elected). To have quota, you do not need support from across the district necessarily. If a corner of the district has a quota worth of votes and the voters there  support a candidate, that candidate will be elected and there is nothing the others elsewhere in the district can do about it. So, at least theoretically, you would not need to campaign across the district. Analysis of results. Academic analysis of voting systems such as STV generally centres on the voting system criteria that they pass. No preference voting system satisfies all the criteria in Arrow's impossibility theorem: in particular, STV fails to achieve independence of irrelevant alternatives (like most other vote-based ordering systems) and monotonicity. Migration of preferences. The relative performance of political parties in STV systems  is analysed in a different fashion from that used in other electoral schemes. For example, seeing which candidates are declared elected on first preference votes alone in the 2012 Scottish local elections, where 1223 members were elected, can be shown as follows: The data can also be analysed to find the proportion of voters who express only a single preference, or those who express a minimum number of preferences, to assess party strength. Where parties nominate multiple candidates in an electoral district, analysis can also be done to assess their relative strength. Other useful information can be found by analysing  terminal transfersi.e., when the votes of a candidate are transferred and no other candidate from that party remains in the countespecially with respect to the first instance in which that occurs: Another effect of STV is that candidates who did well on first-preference votes may not be elected, and those who did poorly on first preferences can be elected, because of differences in second and later preferences. This can also be analysed, again using the 1223 members elected in the Scottish local elections. Some of the leading candidates in the first count are not elected but, comparing the number  to the total number of members elected in these elections, the successful candidates are mostly set in the first count (through the simple mechanics of single voting in multi-member districts), before any vote transfers are done. About ten percent or less of the front runners in the first count are not elected in the end.