User:Jnestorius/STV

The single transferable vote (STV) is a voting system used in multiple-winner elections in which each vote ranks the candidates and may be transferred from a higher- to a lower-preference candidate if the higher-preference candidate has either more than enough votes to be elected or hopelessly few votes. Votes are counted iteratively as follows:

• A quota is determined, directly proportional to the number of valid votes cast and inversely proportional to the number of winning places available.
• On the first count, each vote is allocated in full to its first-preference candidate.
• After each count, any candidate is deemed elected if their vote total reaches the quota.
• If no candidates are declared elected after a count, the candidate with the lowest vote total is eliminated.
• Each count after the first involves the transfer of votes, from a candidate elected or eliminated on a previous count, to remaining candidates. Each such vote goes to the eligible candidate with next highest preference. Candidates previously elected or eliminated are not eligible.
  • From an eliminated candidate, all votes are transferred.
  • From an elected candidate, only surplus votes (exceeding the quota) are transferred.
• Counting ends either:
  • when the number of elected candidates equals the number of winning places; or
  • when the number of remaining candidates equals the number of remaining winning places, in which case all are deemed elected.

Versions of STV may differ in various ways including: the precise formula for the quota; whether transfer of surplus involves transferring a fractional value of all ballots or the full value of a fraction of ballots, and in the latter case, which fraction is selected; whether ballots must rank all candidates or may rank only a subset, and in the latter case, whether the quota is recalculated to exclude exhausted/nontransferable ballots.

STV for elections to deliberative assemblies has been supported by some advocates of proportional representation (PR), in which context the names STV-PR or PR-STV may be used. In practice, district magnitude (number of seats per constituency) tends to be smaller in STV than in list PR systems, which reduces the degree of proportionality achieved. STV advocates are most common in in British-influenced Westminster system democracies; hence it is sometimes called "British PR" in discussions elsewhere. The single-winner analogue of STV is variously called "single-winnner STV", instant runoff voting (IRV) or the alternative vote (AV). The mechanics are simpler: the quota is always a simple majority and there are no surplus transfers, only transfers from eliminated candidates. As a single-winner system, IRV is not a form of PR. STV is not necessarily proportional: counterexamples include the 1930–1935 "commercial members" on Dublin City Council, elected by business ratepayers who had between one and six STV ballots depending on the level of rate paid; the Australian Senate, where each state elects six senators regardless of population; and the vocational panels in Seanad Éireann, where the electoral college consists mainly of members of city and county councils whose sizes are degressively proportional.

STV is used for national legislative elections in Australia (upper house only), Ireland, and Malta. It is used at subnational elections in Scotland, New Zealand, and Northern Ireland.

Largest numbers of winners

• New South Wales Legislative Council two cohorts of 21 elected at large, with group voting tickets since ???
• Irish Seanad
  • Seanad Éireann (Irish Free State)
    • 1922 initial election: 84 electors for 30 seats
    • Irish Seanad election, 1925, large electorae for 19 seats
  • Seanad Vocational Panels 1937-47; 43 seats (10 subpanels) several hundred electorate
• Cork City Council 1929-60, all 21 members elected at once in several cases including
  • 1960 Cork City Council election electorate five figures