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Study Notes

Single Transferable Vote (STV)

AS, A-Level
AQA, Edexcel, OCR, IB

Last updated 22 Mar 2021

Single Transferable vote is used in Northern Ireland for Local and European elections, and for the Northern Ireland Assembly at Stormont, whereit is vitally important that minorities are given fair representation if there is to be any power-sharing. Scottish local councils also adopted it in 2006 and it is also used in Eire, Malta, and Australia (for the Upper House).

STV uses multi-member constituencies: typically 7 or 8 MPs per constituency. The procedure is quite complex:

(i)The voter votes for candidates in order of preference, 1st choice, 2nd choice, 3rd choice etc. He/she can choose from the same party, or from a mixture of parties - so the voter gets a better choice than in the List System.

(ii)The first-choice votes are examined. Any candidate who has gained his "quota" of votes on the first choice is elected. The "quota" is calculated using the Droop formula below or a similar formula:

Quota =({Votes Cast}+1 ) divided by {Number of Seats + 1}

e.g.:in a 7-member constituency of 800,000 voters, all turning out to vote, the quota would be (800000/8 +1) = 100,00. A candidate with more than the necessary quota of 1st choice votes has the surplus redistributed to the 2nd choice, so there is no "wasted vote".


So, in the above example – a 6 member constituency – in the 1nd round McLaughlin and McCrea had beaten the quota and were elected. In the 3rd round nobody had beaten the quota so those at the bottom got eliminated until someone beat the quota. This continued until the 8th round in which the six members were finally elected.

Thus the voter has some say over the choice of candidate. For example, in Northern Ireland in 2003, UUP voters showed a marked preference for individual candidates who had opposed power sharing with SF.

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