In its simplest form, STV means that voters are able to rank candidates in order of preference. With STV, you can rank as many or as few candidates as you wish. To get elected, candidates need to reach a quota of the votes.
Under FPP, you place a tick next to the name(s) of the candidate(s) you are voting for. The candidate(s) with the most votes wins. This is a very simple method of electing candidates and is widely used throughout the world. It was used in New Zealand for parliamentary elections up until the introduction of MMP (Mixed Member Proportional) in the 1996 general election.
In an STV election, the quota is the number of votes a candidate needs to get elected. In the case of single vacancy elections, such as a mayoralty, the quota is referred to as an absolute majority. The quota is based on the total number of votes cast and the number of people needed to be elected to fill all the vacant positions.*
The quota is calculated in the following manner:
- for example, in an election with three vacant positions, where there were 4,000 valid votes, the quota would be:
4000 (Votes) ÷ (3 (Vacancies) + 1) = 1000
So in this case the quota would be 1000.
* A small fraction is added to avoid an equality of votes.
Each candidate has a keep value. It allows them to keep the portion of the vote they need to reach the quota and be elected but allows any extra or surplus votes to be transferred to other candidates, according to voters’ preferences.
For example, if the quota or number of votes required to gain election is 100, and a candidate receives 100 votes, they keep all of those votes, so they have a keep value of 1 (i.e.100%).
But if the candidate received 200 votes, they still only need the equivalent of 100 of those votes to be elected, and the surplus can be transferred to voters’ second preferences. The candidate’s keep value would be 0.5 (i.e. 50%), because that person only needed to keep 50% of all the votes they received in order to be elected.
This means the lower the keep value, the more votes the candidate received. The most popular candidates will have the lowest keep values, because they received so many votes, they only needed to keep a small proportion to gain election.