The Northern Ireland Assembly snap election will bring about the early implementation of plans to reduce the number of Members from 108 to 90.
Under legislation already in place, the next assembly poll will see five Members of the Legislative Assembly, known as MLAs, returned in each of the region’s 18 seats - down from six Members previously.
Elections to the Assembly use the Single Transferable Vote (STV) system, a form of proportional representation involving voting for candidates in order of preference.
This system aims to reduce the so-called “wasted votes” seen in the UK Parliament’s first-past-the-post system, where many electors in traditionally “safe” constituencies find their chosen party never wins and their vote does not count towards electing an MP, or it always wins, piling up majorities of thousands of votes above the number actually needed for victory.
Under STV, instead of a majority of votes, the winning post for the candidates is the quota - the number of valid votes cast divided by the number of seats plus one, plus one vote.
In all of the Northern Ireland constituencies, this comes to a sixth (previously a seventh) of the votes plus one vote. Any candidate passing the quota at any stage during the counting is elected.
Voters are asked to number candidates on the ballot paper in order of preference. The count then involves distributions of votes through many rounds.
Candidates passing the quota are declared elected and the number of their votes above the quota are then distributed to others in accordance with their supporters’ lower preferences as they have expressed on the ballot paper.
Low-scoring candidates are progressively eliminated, with their votes distributed to others in accordance with their supporters’ lower preferences.
This means that the five people elected in each of the 90 seats will be either candidates passing the quota or those remaining when all the other candidates have been eliminated.