The following description is copied from the BC Citizens’ Assembly: Fact Sheet #11 – Proportional Representation by Single Transferable Vote System
PR by Single Transferable Vote
Proportional representation by single transferable vote (PR-STV) is a distinctive variant of proportional representation systems. Like PR-List systems – the larger family of PR systems – the PR-STV system is designed to create a representative assembly which mirrors voter support.
In contrast to PR-List systems which reflect support for political parties, PR-STV is based on voters indicating their preferences for individual candidates.
PR-STV systems ask voters to rank candidates on the ballot – which is called a preferential ballot. Voters’ choice is based on ranking candidates rather than on choosing a party, so voters can choose between candidates from the same party or vote for candidates from different parties.
While the mechanics of vote counting under PR-STV can look complicated, the principle is simple – candidates are elected from multi-member districts in proportion to the electoral support for the candidates expressed in the voters’ preferences.
Candidates may see their major rival as a member of their own party rather than a member of an opposing party. As a consequence, the ability of parties to discipline their candidates is weakened. This limitation on party control of candidates goes a long way to explain why PR-STV has not been popular with governing parties.
Like all PR electoral systems, there are three key elements of the PR-STV system:
- Ballot structure
- District magnitude
- Electoral formula
Ballot structure
Voters are presented with a list – or lists – of candidates, which they rank by numbering the candidates in order of preference using a preferential ballot. Some systems require the voter to make only one choice (Ireland) while others require the ranking of as many candidates as there are seats (Tasmania).
The design of a PR-STV ballot paper is important. The order of candidates and parties on the ballot paper can be contentious. There are wide variations in the way candidates are listed and grouped on the ballot paper. Some jurisdictions use a system of rotating names on the ballot paper to ensure no candidate gets preferential treatment.
District magnitude (DM)
In PR systems, DM – or the number of representatives in a district – can vary from two seats to the total seats in the Legislative Assembly; DM can also vary from electoral district to electoral district. The biggest source of variation with PR-STV is in the district magnitude. Once the number of seats per district drops below five, substantial reductions in proportionality occur if there are a large number of parties.
Electoral formula
In a PR-STV system, candidates are elected as they gain a Quota of votes. A quota can be calculated in various ways, but is essentially the minimum number of votes needed to be elected to a seat.
In successive rounds of counting ballots, candidates are declared elected when they reach a quota of votes, least popular candidates are eliminated and votes are redistributed based on voters’ subsequent preferences. The votes which are redistributed are:
- The surplus votes – those over and above the quota of votes needed to elect a candidate
- Votes from eliminated candidates
This process of redistribution of surplus votes from elected candidates, followed by the exclusion of the least successful candidates and the redistribution of his/her votes, continues until the required number of members is elected.
“Above the Line”
In some PR-STV jurisdictions, voters are able to vote “above the line” – that is, instead of numbering candidates in order of preference, voters have the option of voting for a single party.
This gives the party control over the completion of the whole ballot in a party-preferred order and turns the PR-STV system into something very similar to a PR-List system.
The following description is copied from the Electoral Reform Society – UK
Single Transferable Vote
How does the Single Transferable Vote work?
The Single Transferable Vote (STV) is a form of proportional representation where you rank the candidates in constituencies that elect multiple MPs.
Candidates don’t need a majority of votes to be elected, just a known ‘quota’, or share of the votes, determined by the size of the electorate and the number of positions to be filled.
Each voter gets one vote, which can transfer from their first-preference to their second-preference, so if your preferred candidate has no chance of being elected or has enough votes already, your vote is transferred to another candidate in accordance with your instructions. STV thus ensures that very few votes are wasted, unlike other systems, especially First Past the Post, where only a small number of votes actually contribute to the result.
Pros and cons of the Single Transferable Vote
The case for STV
STV gives voters more choice than any other system. This in turn puts most power in the hands of the voters, rather than the party heads, who under other systems can more easily determine who is elected. Under STV MPs’ responsibilities lie more with the electorate than those above them in their party.
Fewer votes are ‘wasted’ (i.e. cast for losing candidates or unnecessarily cast for the winner) under STV. This means that most voters can identify a representative that they personally helped to elect. Such a link in turn increases a representative’s accountability.
With STV and multi-member constituencies, parties have a powerful electoral incentive to present a balanced team of candidates in order to maximise the number of higher preferences that would go to their sponsored candidates. This helps the advancement of women and ethnic-minority candidates, who are often overlooked in favour of a ‘safer’ looking candidate.
STV offers voters a choice of representatives to approach with their concerns post-election, rather than just the one, who may not be at all sympathetic to a voter’s views, or may even be the cause of the concern.
Competition is generally a good thing and competition to provide a good service to constituents is no different.
Parliament is more likely to be both reflective of a nation’s views and more responsive to them. Parties are broad coalitions, and can have a markedly broad range on lots of issues. With only one party person per constituency, the representatives elected may well not reflect the views of their electorate. STV would help voters to pick a candidate who most closely reflects their own views and values.
Under STV, as opposed to hybrid systems such as AMS, all MPs are elected on the same basis, thus lessening the chances of there being animosity between them.
There are no safe seats under STV, meaning candidates cannot be complacent and parties must campaign everywhere, and not just in marginal seats.
When voters have the ability to rank candidates, the most disliked candidate cannot win, as they are unlikely to pick up second-, third- and lower-preference votes.
By encouraging candidates to seek first-, as well as lower-preference votes, the efficacy of negative campaigning is greatly diminished.
There is no need for tactical voting.
There is a more sophisticated link between a constituency and its representative. Not only is there more incentive to campaign and work on a more personal and local level, but also, the constituencies are likely to be more sensible reflections of where community feeling lies. For example, there is more of an attachment to the City of Leeds or the City of Manchester, than there is to, say, Leeds North East or Manchester Withington, whose boundaries have a habit of changing fairly regularly anyway.
The arguments against STV
In sparsely populated areas, such as the Scottish Highlands, STV could lead to very large constituencies.
The process of counting the results takes longer under STV, meaning that results cannot usually be declared on the same night as the vote took place. This can be combated with electronic ballot paper scanners.
A voting system that allows voters to rank candidates is prone to so-called ‘Donkey voting’, where voters vote for candidates in the order they appear on the ballot. Names on ballot papers have to be batch printed using a method known as Robson Rotation.
Voters only tend to come into contact with candidates at election time, whereas people in the party know them much better. It could be argued, therefore, that a system that allows a political party to parachute its preferred candidates into safe seats is better than one that leaves the choice more in the hands of the voters.
In large multi-member constituencies, ballot papers can get rather big and confusing.