Single transferable vote

Quota and vote transfers

STV systems primarily differ in how they transfer 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 so that no more candidates can reach quota than there are seats to be filled. The Droop quota is the most commonly used quota. It being relatively low means that the largest party is likely to take the majority of the seats in a district. The Hare quota, which was used in the original proposals by Thomas Hare,[6] ensures greater representation to less-popular parties within a district.

The easiest methods of transferring surpluses involve an element of randomness; partially random systems, such as the Hare system, are used in the Republic of Ireland (except Senate elections) and in Malta, among other places. The Gregory method (also known as Newland-Britain or Senatorial rules) eliminates randomness by allowing for the transfer of 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.[7] 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[8] 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.[9] This has subsequently (since 1998) been used by the John Muir Trust for electing its trustees.[10]

Example

Suppose an election is conducted to determine what three foods to serve at a party. There are 5 candidates, 3 of which will be chosen. The candidates are: Oranges, Pears, Chocolate, Strawberries, and Hamburgers. The 20 guests at the party mark their ballots according to the table below. In this example, a second choice is made by only some of the voters.

# of guests	x x x x	x x	x x x x x x x x	x x x x	x	x
1st preference
2nd preference

First, the quota is calculated. Using the Droop quota, with 20 voters and 3 winners to be found, the number of votes required to be elected is:

${\displaystyle Q_{\operatorname {Droop} }=\operatorname {floor} \left({20{\mbox{ (votes cast)}} \over {3{\mbox{ (seats to fill)}}}+1}\right)+1=6{\mbox{ (votes required)}}}$.

When ballots are counted the election proceeds as follows:

Candidate						Result
Round 1	x x x x	x x	x x x x x x x x x x x x	x	x	Chocolate is declared elected, since Chocolate has more votes than the quota (with six surplus votes, to be precise).
Round 2	x x x x	x x	x x x x x x	x x x x x	x x x	Chocolate's surplus votes transfer to Strawberry and Hamburgers in proportion to the Chocolate voters' second choice preferences, using the formula: ${\displaystyle \left({{\text{votes for second preference}} \over {\text{total votes for Chocolate}}}\right)\times {\text{surplus votes}}}$ In this case, 8 of the 12 voters for Chocolate had the second preference of Strawberries, so (8/12)•6 = 4 of Chocolate's votes would transfer to Strawberries; meanwhile 4 of the 12 voters for Chocolate had Hamburgers as their second preference, so (4/12)•6 = 2 of Chocolate's votes will transfer to Hamburgers. Thus, Strawberries has 1 first-preference votes and 4 new votes, for an updated total of 1 + 4 = 5 votes; likewise, Hamburgers now has 1 + 2 = 3 votes; no other tallies change. Even with the transfer of this surplus no candidate has reached the quota. Therefore, Pear, which now has the fewest votes (after the update), is eliminated.
Round 3	x x x x x x		YES	x x x x x	x x x	Pear's votes are transferred in proportion to the second-preference options of voters of Pear, i.e. only Oranges in this case, which gives Oranges 2 more votes. Oranges now totals 4 (original) + 2 (new) = 6 votes, reaching the quota; so, Oranges is elected. Orange meets the quota exactly, and therefore has no surplus to transfer.
Round 4	YES		YES	x x x x x	x x x	Neither of the remaining candidates meets the quota, so again the lowest candidate (in this case Hamburgers) is eliminated. This leaves Strawberries as the only remaining candidate, so it wins the final seat (despite not satisfying the quota). (If there were still unfilled seats, Hamburgers' votes would be transferred proportionately based on next preferences, if there were any indicated. So Chocolate-then-Hamburgers votes that had gone to Hamburgers cannot be transferred again as only two preferences were selected. And no one who voted for Hamburgers originally gave a second preference.)

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.

History and current use

Carl Andræ

The concept of transferable voting was first proposed by Thomas Wright Hill in 1819. The system remained unused in public elections until 1855, when Carl Andræ proposed a transferable vote system for elections in Denmark, and his system was used in 1856 to elect the Rigsraad and from 1866 it was also adapted for indirect elections to the second chamber, the Landsting, until 1915.[11]

Thomas Hare

Although he was not the first to propose transferable votes, the English barrister Thomas Hare is generally credited with the conception of STV, and he may have independently developed the idea in 1857. Hare's view was that STV should be a means of "making the exercise of the suffrage a step in the elevation of the individual character, whether it be found in the majority or the minority." In Hare's original system, he further proposed that electors should have the opportunity of discovering which candidate their vote had ultimately counted for, to improve their personal connection with voting.[6] At the time of Hare's original proposal, the UK did not use the secret ballot, so not only could the voter determine the ultimate role of their vote in the election, the elected MPs would have been able to determine who had voted for them. As Hare envisaged that the whole House of Commons be elected "at large" this would have replaced geographical constituencies with what Hare called "constituencies of interest" – those people who had actually voted for each MP. In modern elections, held by secret ballot, a voter can discover how their vote was distributed by viewing detailed election results. This is particularly easy to do using Meek's method, where only the final weightings of each candidate need to be published. The elected member is, however, unable to verify whom their supporters were.

The noted political essayist John Stuart Mill was a friend of Hare's and an early proponent of STV, praising it at length in his essay Considerations on Representative Government, in which he writes: "Of all modes in which a national representation can possibly be constituted, this one affords the best security for the intellectual qualifications desirable in the representatives. At present... the only persons who can get elected are those who possess local influence, or make their way by lavish expenditure...."[12] His contemporary, Walter Bagehot, also praised the Hare system for allowing everyone to elect an MP, even ideological minorities, but also argued that the Hare system would create more problems than it solved: "[the Hare system] is inconsistent with the extrinsic independence as well as the inherent moderation of a Parliament – two of the conditions we have seen, are essential to the bare possibility of parliamentary government."[13]

Advocacy of STV spread throughout the British Empire, leading it to be sometimes known as British Proportional Representation. 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".[14] 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.[15]

STV in large constituencies permits an approach to the Hare-Mill-Wells ideal of mirror representation. The UK National Health Service used to elect, First Past The Post, all white male General Practitioners. In 1979, STV proportionally represented women, immigrants and specialists, to the General Medical Council.[16]

Australian Senate ballot paper used in Victoria for 2016

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 in order 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[17] 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),[18] followed by the Single Transferable Vote being introduced for the New South Wales Legislative Council in 1978,[19] the Western Australian Legislative Council in 1987[20] and the Victorian Legislative Council in 2003.[21] The Single Transferable Vote was also introduced for the elections to the Australian Capital Territory Legislative Assembly after a 1992 referendum.[22]

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 and the park board in Minneapolis, Minnesota. STV has also been adopted for student government elections at several American universities, including Carnegie Mellon,[23][24] MIT, Oberlin, Reed, UC Berkeley, UC Davis, Vassar, UCLA, Whitman, and UT Austin. Legislation (HR 3057), was introduced in Congress in June 2017 that would establish STV for US House elections starting in 2022.[25]

Pros and cons of STV

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 single 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),[32] the Electoral Reform Society in the United Kingdom[33] and FairVote in the USA (which refers to STV as fair representation voting[34] and instant-runoff voting as "ranked-choice voting",[35] although there are other preferential voting methods that use ranked-choice ballots).

Its 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 § Voting).[36]

Others see a vote transfer process that is more time-consuming than in first-past-the-post elections where the result is known within a few hours and say it is not worth using STV just to have more proportional results. However, STV's supporters say that some winners are known in the same period as under FPTP, and that with delays under FPTP caused by mail-in or absentee ballots, any delays in an STV scenario are not noticeable or are no great hardship.

Issues

Analysis of results

Academic analysis of voting systems such as STV generally centers 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.

See also

Notes

References

Further reading

External links

• ACE Project
• A concise STV analogy – from Accurate Democracy
• Accurate Democracy lists a dozen programs for computing the single transferable vote.
• Australia's Upper Houses – ABC Rear Vision A podcast about the development of Australia's upper houses into STV elected chambers.