Wednesday, September 01, 2010

STV geeking

Election geek alert: I just found this site on STV (Single Transferable Vote) which allows you to experiment with various permutations of voting in an STV election (as well as having a step by step guide on how it actually works).

While the guide admirably simplifies the whole process in the process it does obscure exactly how complex an STV election is to actually count as people sadly/happily don't vote en bloc the way they do in the site's examples - and it's certainly not obvious to the people voting in an STv election exactly how to use their vote most effectively to get the result they want.

STV is best used for multi-member committees and the like but you often see it used to create ordered lists (for example the Greens use it for their European and London Assembly Lists) which isn't a brilliant use for it.

Some people say that it allows you to vote for exactly how you want to see the list ordered - but that's not true at all. Unlike AV in STV only part of your vote transfers over to your secondary preferences - so the best tactical approach is to ask yourself "who needs my vote the most" because whoever you've put in third place is likely to only get a fraction of your support - if it goes that far.

Anyway, I'm being a geek and thought I'd pass on the nice little tool I found.


Shahrar Ali said...

Jim, nice site, but simple to follow? :) I fear you may have misunderstood something about how the STV system is used, and effectively so, by the Greens. If you’re using it to order a set of candidates on a multiple vacancy list (e.g. Euro list), then you can think of it as a series of elections, for first place (by single tranferable vote with a quota), then for second place single transferable vote, then for third place, etc, until you’ve filled all the vacancies (plus any reserves). The beauty of STV, then, is that you can indeed express your preferences as you would like your list to be ordered – on your ballot paper of course. It doesn’t make sense to try to vote tactically in such an election. In your example, if you want somebody to come third on the list, then put them third, not first. Put first, who you want to come first. By such means, Greens have successfully returned outstanding elected members in Euro and regional elections in successive terms. The real problem, I would say, is that voters are so used to thinking tactically (such as in FPTP) that they sometimes have trouble imagining what it’s like to vote for what they actually want or believe in. Much better than this site, I think, is to observe an actual STV contest being counted – with both manual and computerised stages. It’s rewarding, even sobering, to see our best available system in action. Ps. Whilst I’m here, congrats on topping the Green Bloggers poll (I wonder what system was used :)

Jonathan Lundell said...

The tactic you're referring to falls into the class of strategies known as free riding. There's a nice piece on it here:

Like many forms of tactical voting, it depends on having good knowledge as to the behavior (and not just the preferences) of your fellow voters. If you're wrong about the popularity of your first choice, or your fellow voters decide to engage in the same strategy, you're screwed.

Allow me to toot my own horn. I'm convinced, and I hope to convince you and others, that STV is not as complicated as it it typically made out to be.

Have a look at and see if you don't agree.