I’m placing this in After Hours rather than say, the politics forum, as I want this to be seen by a wider audience.
The STV in PR-STV stands for Single Transferrable Vote and that is what we have in a nutshell. Let me explain.
This is not the Eurovision. When you rank your preferences, they don’t all get varying levels of vote scores depending on what number preference you gave them. At any one time your vote can only be counted for a single candidate. At the count centre this is done by physically placing your ballot paper into a pile along with all of the other votes for that candidate. On the first count this will be dictated by whoever you gave your #1 preference to. At that stage, they don’t even look at the rest of the numbers that you have written down so all that matters at this point is your #1. For this reason, your #1 preference is significantly more important than your lower preferences. At the end of the first count, candidates will begin to be either elected or eliminated from the process and that’s when the transfers kick in.
In every constituency there will be a magical number that represents the number of votes that a candidate needs to be elected. This is known as The Quota. The actual value of this depends on how many people voted in the constituency and the number of seats on offer. It’ll be a different number in each constituency but it’s typically around the 11,000 mark. If any candidate gets more votes than the quota after any count, then they’re elected. If, on the other hand, nobody has reached the quota then the candidate with the lowest vote total is eliminated. In both of these scenarios votes will subsequently be transferred. Let’s look at these in turn:
When a candidate is eliminated:
The people in the count centre will go through all the ballots in the eliminated candidates pile and look for the next, lower numbered preference who is still in the race (ie not already eliminated or elected). They will then physically take that ballot and transfer it into the pile of that next numbered candidate, which adds to their vote total. If they don’t find any further preferences who can be transferred to on a ballot then the vote is effectively dead (The technical term is Non-Transferable and it’s a shame when this happens as that voter has lost their power to elect anyone else with their ballot).
When a candidate is elected:
When a candidate is elected only some of their votes are transferred (usually a small fraction). Imagine the quota is 10,000 votes and the candidate has 12,000 votes after a count has been completed. The rule is that a candidate only needs the quota number of votes to be elected. That means that they can afford to give away their excess votes to other candidates. In this example 2,000 of their votes will be transferred. Which 2,000 votes of their 12,000 are chosen to be transferred is frankly beyond the scope of this explainer.
The counts and transfers continue until all the seats have been allocated.
I want to finish by addressing some common questions or comments that I have heard over the years:
|I would like to vote for a candidate from Party XYZ but I know that she has no hope of being elected. Am I wasting my vote?|
|I really hate that candidate from party QRS. How do I make certain that I don't help to elect them by accident?|
|I like that candidate. I'm thinking of giving him a vote, either my #3 or #4|
The thing is though that when they do transfer they are very important and for this reason you should always have plenty of lower preferences. Just don't fool yourself into thinking that they'll be used most of the time. This is the reason why the #1 preference is so massively important and why candidates explicitly ask for it.
I could write a lot more about this but this post has already gotten way longer than I wanted. I can answer any follow up questions in the thread below. My hope is that this will have helped people to understand things a little better.