Elections to the Northern Ireland Assembly use the Single Transferrable Vote (STV) system. This is a way of electing MLAs that fully ensures that the number of seats a party wins is directly in proportion to the share of votes. STV does this by using a very accurate but complicated counting system.
In this system, multiple representatives are elected in each constituency. In each of these areas, 6 MLAs will be elected.
As a voter, you will get one ballot paper with all the candidates listed. As you’re electing more than one person, there is likely to be more than one person from each party listed. Instead of putting an X next to the people you want to vote for, you mark your choices in order of preference, so 1 (first choice), 2 (second choice) and so on. You can rank as many or as few candidates as you want, and they can be from any number of different parties, or all from the same one. The more candidates you give a rank to, the greater the chances of your vote making a difference.
The votes are counted in such a way so as to elect the people who get the most votes, but also making sure that each party wins a similar share of seats to the share of the votes they received. Overall, if 60% of people vote for candidates from Party A, Party A should finish up with around 60% of the seats.
The actual counting system is complex. Essentially, once all the votes are in, election specialists work out how many votes a candidate needs to get in order to be elected, the “quota”, basically the winning line. Any candidates who got enough first choice votes (“Number 1’s”) to take them past this winning line are elected immediately. After that, the candidates with the fewest votes get knocked out, and their vote is transferred (hence ‘Single Transferrable Vote’) to the second/third/fourth/etc choice candidate as appropriate. If any remaining candidates get enough transferred votes to take them over the winning line, they also get elected. This process of eliminating the lowest candidates, and transferring their votes to the remaining candidates goes on until all the seats are filled.
Single Transferable Vote balances the need for ‘local’ representatives, who are tied to a constituency, along with providing the best chance that the number of seats won by each party is as close as possible to the number of votes they have won overall. It also means that, because of the complicated counting process, every vote counts.