on 16-Apr-2021 (Fri)

The single transferable vote (STV) is a voting system designed to achieve or closely approach proportional representation through the use of multiple-member constituencies and each voter casting a single ballot on which candidates are ranked. The preferential (ranked) balloting allows transfer of votes to produce proportionality, to form consensus behind select candidates and to avoid the waste of votes prevalent under other voting systems.^[1] Another name for STV is multi-winner ranked-choice voting.^[2]

Each elector marks their ballot for the most preferred candidate and also marks back-up 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 a back-up preference, with the vote being assigned to the voter's second, third, or lower choice if possible (or under some systems being apportioned fractionally to different candidates).

Under STV, district elections grow more proportionally representative in direct relation to increase in the number of seats to be elected in a constituency – the 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 \({\displaystyle ({\rm {\mbox{valid votes cast}}})/({\rm {\mbox{seats to fill}}})}\), a candidate or party needs 33 percent of the votes 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.

STV also provides approximately proportional representation, ensuring that substantial minority factions have some representation. No one party or voting block can take all the seats in a district. The key to STV's achievement of proportionality is that each elector (voter) only casts one single vote, in a district election electing multiple winners.

Where there are more candidates than seats, the least popular is eliminated and their votes transferred based on voters' marked back-up preferences.

STV enables voters to vote across party lines, to choose the most preferred of a party's candidates and vote for independent candidates, knowing that if the candidate is not elected their vote will likely not be wasted.

During the count, as candidates are elected or eliminated, surplus or discarded votes that would otherwise be wasted are transferred to other candidates

Proportional representation (PR) characterizes electoral systems in which divisions in an electorate are reflected proportionately in the elected body.^[1] The concept applies mainly to geographical, and to ideological partitioning of the electorate