The basic idea is that you mark your preferences in order. This is simple enough to grasp. What isn't is when all the first preferences are added up and there is no majority (more than 50%), what happens next. The Eelctoral Reform Society has it as this:
If no candidate gains a majority on first preferences, then the second-preference votes of the candidate who finished last on the first count are redistributed. This process is repeated until someone gets over 50 per cent.To me that is just not clear about what is going on. I spent over an hour on the phone and still did not understand. So we began our own based around Ice Cream to help demonstrate what is going on. Full details can be found on Kitty's blog. It also includes the raw data and my Python implementation amongst others. I recommend you check it out, but I'll come back to it later.
The way I found best to understand this was this:
- Imagine your ballot paper is a queue, you choose who is first, second, third and so on in that queue.
- When the votes are counted, you count ONLY the first person of each queue.
- If one candidate has more that 50%, that candidate wins. If not, the lowest candidate is eliminated, and removed from ALL queues, meaning anyone behind them moves forward into their place. Any that were 2nd choices have now been effectively added to the first choices.
- Go to 2.
So, blue has the least 1st preference votes, so is eliminated from the running, leaving this:
Now all the remaining votes move forward, like so:
And we now recount the votes in the green section. If there is still no majority, you continue eliminating the last place and moving votes forward until you do. In this case red wins even though all parties had the same number of votes, because it had the higher preference votes.
If a vote runs out of preferences, it is just discarded (and the quota is decreased accordingly) and the rules for tie-breaking depend upon the rules of the particular ballot you are participating in.
Hopefully you've understood that analogy. Now I'll talk some more about our test ballot. We took 70 votes for 5 candidate flavors of ice cream. Now using First Past The Post, Mint won, with 22 votes for and 44 votes against (the other 4 ballots were spoiled and invalidated). So more people would prefer not to have Mint than to have it.
This is where Alternative Vote comes in. The lowest vote was Strawberry, so we removed it from the votes, and moved the 2nd preferences forward. This was followed by the elimination of Fudge and Chocolate. What this left us with was Vanilla as the winner. It may not have had the most first preference votes, but because more people would accept it than mint (33 instead of 22), it's the least objectionable option, something the majority can enjoy.
So what does AV get us? More than one vote? No. Our first choice? Not necessarily. Someone we'd prefer over another candidate? Most definitely.
I'm not going to try sway anyone's vote for May 5th, everyone is entitled to their own opinion. Whatever your view, I hope this has helped you to understand the counting process under AV.