How the Single Transferrable Vote system works
Posted by Feargal O'Kane on Mar 01 2007 under Election |
The way people vote in a Northern Ireland Assembly election differs substantially from any other election in the UK. At most elections the voter simply puts a cross next to the person they want to vote for. For the Northern Ireland Assembly however, the voter must rank all the candidates 1, 2, 3 and so on.
For example, you would put a 1 next to your first choice, a 2 next to your second and so on until you run out of numbers and candidates. This is called preferential voting as the voter is giving not just their first choice, but also their second and third choices right down to their last. It should be said that the voter is not compelled to use all their votes so if they want to vote for just 10 out of 15 candidates they can do so.
It would be fair to say that the Single Transferable Vote (STV) system is the most complicated electoral system to explain there could ever be.
Although the actual vote itself is relatively straightforward (ranking candidates instead of putting a single cross), counting the votes and working out who has won is an entirely different matter.
For the purposes of clarity, throughout this explanation we will pretend that there are 4 parties - Beef, Lamb, Pork and Chicken, and that the Assembly constituency, called Casserole (with 50,000 votes cast) has 6 MLAs to elect.
Why the STV system is used and how it works
If the Northern Ireland Assembly was elected on the usual single-cross system (known as a plurality system or First Past the Post), there would be single constituencies represented by a single MLA. To get elected, that person would simply require more votes than anyone else, for example, if the Beef candidate got 15,500 votes, Lamb 14,500, Pork 16,000 and Chicken 4,000, the winner would be Pork, even though only 32% of voters voted for Pork and 68% voted against Pork, be it for Beef, Lamb or Chicken.
The significance of the nationalist / unionist divide in Northern Ireland meant that it was thought best to have an electoral system where the views of all sections of the community would have an impact on the final result. STV is deliberately used to force parties to share power. As a safeguard, the two largest parties in the Assembly must both agree to form an Executive - this being the reason why the Assembly has been suspended as the UUP, then the DUP, refused to work with Sinn Féin.
The first step is to have multimember constituencies where each constituency has six people representing it and the second is to have voters ranking candidates rather than voting for just their first preferences.
In our example, the Casserole constituency now needs to elect six MLAs rather than one and the 50,000 votes are all ranked. Each of the parties has put up six candidates, giving us twenty-four candidates in total.
The very first thing that is worked out is called the Droop Quota - the number of votes needed to elect each MLA. This is the total number of votes cast divided by the number of vacancies plus one, plus one; or, in terms of our example here, (50,000/ (6+1))+1, or 7,143.
That means that for a candidate to be elected they must get 7,143 votes. It is theoretically possible that 6 candidates could get that number of first preference votes straight away but this would be highly unlikely and that is where the second, third and so on preferences come into play.
Let us assume that one of the Lamb candidates is especially popular and gets 8,000 first preference votes. His 5 colleagues get 1,300 each, giving us the 14,500 first choicevotes for the Lamb Party in our example.
As the Lamb candidate (candidate LA) has passed the quota, he is elected straight away but he has 857 ’surplus’ votes. These votes are therefore ‘transferred’ to other candidates - the first preferences for LA now mean nothing and so the surplus votes are given to the second preference on those ballot papers. If we assume that those 857 votes go evenly around his Lamb Party colleagues, they now have 1,300 + 171 = 1,471 votes each, with one candidate getting 1,473 (you cannot get half a vote!). These candidates are clearly way off reaching the quota and so even though we have transferred LA’s surplus, there is still a long way to go for any of his colleagues to get elected with him.
If no other candidates from any party gets the required 7,143 votes, the candidate with the fewest number of first preference votes drops out and his votes are then redistributed according to their second preference.
This process continues for a very long time until all six places are filled up. In this example, if we followed it all the way through, the most likely result would be that Beef, Lamb and Pork would all have two MLAs elected and that Chicken would have none.
Therefore, whereas under the usual system Pork would have been elected with 32% of the vote, under STV, three parties will be represented, making up 92% of the vote with only the Chicken Party excluded.
Taken from ‘The Untangled Web’ guide to the Assembly elections by Projecting Politics.
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