How Northern Ireland elects its Assembly
Northern Ireland Assembly elections use the Single Transferable Vote (STV). Instead of placing one X beside one candidate, voters rank candidates in order of preference — 1, 2, 3 and so on. Voters can rank as many or as few candidates as they wish.
There are 18 constituencies, each electing five MLAs. A quota is calculated from the number of valid votes and seats available. Candidates who reach it are elected. Surplus votes from elected candidates and votes from eliminated candidates can then transfer according to later preferences.
Why first preferences are not the whole result
A candidate's first-preference total matters, but STV counting can continue through multiple stages. Later preferences can therefore help determine who wins the remaining seats. That is why Northern Ireland election coverage often reports both first-preference vote shares and final seats.
The most recent Assembly election was held in May 2022, when Sinn Féin became the largest party by seats with 27. The 2017 election had already reduced the Assembly from 108 to 90 MLAs.