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The Supplementary Vote (SV) is a Voting System used for the election of a single candidate. Under SV each voter ranks from among the list of candidates a first and a second preference. If no candidate receives an absolute majority of votes on the first count all but the two leading candidates are eliminated and the second preferences of those who voted for eliminated candidates are redistributed to help determine a winner. It is intended to make it likely that a candidate will be elected by an absolute majority (i.e. more than half) of voters. It is currently used in all elections for directly elected mayors in England , including the Mayor Of London . The Supplementary Vote is the same as Instant Run-off Voting (also known as the Alternative Vote) except that there are only two rounds of counting and the voter is restricted to expressing only a first and a second preference. It can also be considered a special form of the Two Round System , in which both 'rounds' occur without the need for voters to go to the polls twice. VOTING AND COUNTING Each voter ranks at least one and no more than two candidates in order of preference. In other words she must give a '1' to her first preference and a '2' to her second choice. In this respect it is the same as other Preferential Voting Systems except that the voter is only permitted to express two preferences, and is not allowed to rank all of the candidates. In the first round of counting only first preferences are tallied. If any candidate has an absolute majority at this stage then are declared elected. If no candidate has a majority then all candidates except the two with most first preferences are eliminated and the count proceeds to a second round. In the second round any voter whose first preference has been eliminated has his vote transferred to the candidate of his second preference (but only if his second choice has not also been eliminated). The candidate with the most votes is then declared elected. EXAMPLE Imagine an election in which there are three candidates: Andrew, Brian and Catherine. There are 100 voters and they vote as follows: 1. To begin the count first preferences are counted, and the tallies stand at:
2. No candidate has an absolute majority of votes (this would be 51), so the two candidates with most votes proceed to a second round and Brian, who has the fewest votes, is excluded. All of Brian's supporters have given Andrew as their second preference, so his votes all transfer to Andrew. The tallies then become:
Result: Andrew has the most votes so is declared the winner. COMPARISON WITH INSTANT RUN-OFF VOTING The Supplementary Vote differs from instant run-off voting (IRV) in two ways: voters are only permitted to express two preferences, and all but the top two candidates are eliminated after the first round. Under IRV only one candidate is eliminated after each round, and as many rounds occur as are necessary to give one candidate an absolute majority. These differences mean that SV and IRV can produce different results. Restricting a voter to two preferences means that it might not be possible to transfer her vote to any candidate in the final round–if this occurs her vote is said to be 'exhausted'. If voters are permitted to rank all of the candidates then this cannot occur and every voter will have a chance to contribute to electing a winner in the final round. The Contingent Vote is an electoral system identical to the Supplementary Vote except that voters are permitted to rank all candidates; because of this SV and the contingent vote often produce different results. Results of SV elections are also influenced by the fact that there are only two counts. Because all but two candidates are eliminated in the first round it is possible for a candidate to be eliminated who would have gone on to win had he been allowed to receive transfers in later rounds. This effect differentiates IRV from both SV and the contingent vote. Example Imagine an election in which there are four candidates: Andrea, Brad and Carter and Delilah. There are 100 voters. If they were asked to rank all of the candidates in order of preference then their preferences would be as follows: However under the Supplementary Vote the voters are only permit to express their top two preferences, so they vote as follows: 1. To begin the count first preference votes would be tallied, and found to be as follows:
2. No candidate has an absolute majority so Andrea and Brad would proceed to the second round, while the other two would be excluded. Carter supporters all have Brad as their second choice so their votes would now transfer to Brad. However Delilah voters have Carter as their second choice so, because he is no longer in the count, their votes cannot be transferred to anyone. After the second count the results are therefore:
Result: Andrea has the most votes so is the winner. In the example the result is effected by the fact that Delilah supporters are only allowed to express two preferences, and therefore their votes cannot be transferred to either of the two candidates in the last round. The third preference of Delilah supporters was for Brad. If this preferences had been taken into account then Delilah's votes would have transferred to Brad in the final round and Brad would have been the winner instead of Andrea. For the reason given if the contingent vote had been in the example instead of SV then Brad would have been elected. The example is also influenced by the fact that their are only two rounds. If IRV were used in the example, instead of SV or the contingent vote, then Carter would have been elected. This is because after the first round only Delilah would have been eliminated. His votes would then transfer to Carter and the tallies would become:
Brad would then be eliminated and his votes would transfer to Carter, who would then have an absolute majority of votes. HISTORY AND CURRENT USE , the first directly elected Mayor of London. In England elected mayors are chosen by means of the Supplementary Vote.]] The Supplementary Vote has been used since 2000 to elect the Mayor Of London . At the start of the twenty-first century it was also in use for the direct election of eleven English mayors. The system was invented in 1993 by the Plant Commission . This was a commission established by the Labour Party , which was then in opposition, to recommend a new voting system for the British Parliament . Instead of suggesting an already existing system the Commission chose to devise its own. However it never became official Labour Party policy to introduce the Supplementary Vote for national elections in the United Kingdom . Prior to 2000 there were no directly elected mayors in England. When direct elections were introduced for some mayors it was decided to use SV. A system similar to the Supplementary Vote has been used to elect the President Of Sri Lanka since 1982 . Under the Sri Lankan System voters are permitted to express, from among the list of candidates, not just a first and second but also a third preference. POTENTIAL FOR TACTICAL VOTING Under the Supplementary Vote, unlike under instant run-off voting, a voter will not influence the final result of an election unless she expresses either a first or a second preference for one of the two leading candidates. Furthermore, her first preference is unlikely to be of influence unless it is given to one of the three leading candidates. These two factors encourage voters to vote tactically rather than sincerely. More broadly, the Supplementary Vote is vulnerable to the tactics of 'push over' and 'compromise'. Under the Supplementary Vote compromising occurs where a voter gives a first or second preference to a candidate not because they necessarily support them, but as a way of avoiding the election of a candidate who they dislike even more. SV is more vulnerable to compromising than IRV. In the first example given in this article if a large number of Catherine supporters had 'compromised', and given a first preference to Brian, then Brian would have been elected instead of Andrew, a candidate who Catherine supporters dislike even more. This tactic would have been effective under IRV as well as the Supplementary Vote. In the second example Delilah voters, had they predicted that Carter would not make it to the second round, could have compromised by giving their second preferences to Brad, and thereby have ensured his election. This would not have been an unnecessary tactic under IRV because Delilah supporters could have given Brad as a third choice. However SV is less vulnerable to the tactic of'compromise than the ' First-past-the-post ' (plurality) system. This is because SV's system of transferring votes means that even if a voter's first choice is unlikely to be elected, her vote may still have a chance to be transferred to her second choice (provided her second preference has survived to the second round). In the first example given above Catherine would have won under the plurality system because she has more votes than any other candidate. However Brian voters would have been able to ensure the election of their second choice, Andrew, by voting tactically for Andrew instead of Brian. This tactic is not necessary under the Supplementary Vote because the votes of Brian supporters will end up with Andrew anyway–when Brian is eliminated they will transfer to him. Both IRV and the Supplementary Vote are vulnerable to the 'push over' tactic. 'Push-over' is a tactic by which a voter insincerely ranks an unpopular 'push-over' candidate higher than her real first choice. The purpose of voting for the 'push-over' is to ensure that it is this weak candidate, rather than a more popular rival, that remains to challenge her preferred candidate in the second round. By supporting a push-over candidate it is hoped to eliminate a stronger candidate who might have gone on to win the election. Under the Supplementary Vote a voter uses the tactic by giving her first preference to a 'push over' and her second preference to the candidate she really supports. The push-over tactic requires voters to be able to reliably predict how others will vote. It runs the risk of backfiring, because if the tactical voter miscalculates then the candidate intended as a push-over might end up actually beating the voter's preferred candidate. It also requires voters to understand the tactic and be aware that it exists. For these reasons some doubt that push-over is likely to be a factor in real elections. Because under SV, as under IRV, it is paradoxically possible to harm the chances of a candidate by ranking them ''higher'', or to aid the chances of a candidate by ranking them ''lower'', the system is said to fail the Monotonicity Criterion . IMPACT ON FACTIONS AND CANDIDATES The Supplementary Vote is not a form of Proportional Representation , and were it used to elect a council or legislature, it could be expected to overrepresent larger parties at the expense of smaller ones in the same manner as other systems based on single winner elections, such as 'first past the post' and instant run-off. Like IRV, the SV is said to encourage candidates to seek support beyond their core base of supporters in order to secure the second preferences of the supporters of other candidates. This is said to create a more conciliatory campaigning style among candidates with similar policy platforms. SV is also likely to improve the chances of 'third party' candidates by encouraging voters who wish to do so to vote sincerely for such candidates where under systems such as 'first past the post' they would be discouraged from doing so for tactical reasons. These potentially positive effects will be moderated, however, by the strong incentives the Supplementary Vote creates for voting, in most circumstances, only for candidates from among the leading three. The Electoral Reform Society criticised the Supplementary Vote following the mayoral election in Torbay in October 2005 , claiming that 43.5% of second preference votes were ignored as not being given to either of the top two placed candidates, disadvantaging supporters of non-party candidates. NOTE |