Tuesday 26 April 2011

Once more, with feeling

An abstract avoids prejudice but fails to engage, an analogy whilst having sound maths is vulnerable to complaints of being too simple. And an illustration using our political parties is at risk from the same criticism, but I thought I’d re-write the case of an alternative vote (AV) that leads to an ‘unfair’ result. The point isn’t so much “Party A voter would never vote for Party B”, but that they might express such a preference in order to keep out a substantially worse candidate. For instance, as someone who generally votes Conservative, I have no fondness for either Labour or the Liberal Democrats; however I wouldn’t hesitate to vote for either of these options to ensure exclusion of the BNP. Here’s the example:

There are four political parties standing in your constituency; in alphabetical order of party (and as it happens, candidate): BNP, Conservative, Labour and Liberal Democrat.

48,226 votes are cast.

The BNP receives 2,296 first preferences, of those votes the second preference where stated is split 978 for Conservative and 620 for Labour. 20,668 people vote Liberal Democrat; it subsequently turns out their second choice isn’t relevant – likewise for the 16,075 who vote Labour. The vast majority of the 9,187 people who vote Conservative don’t really care for the other two main parties, which shouldn’t surprise anyone, however most of them also loathe the BNP.

That’s understandable, and the best way to express this is a feature of AV that isn’t afforded by our current first-past-the-post (FPTP) system; the ability to vote against one party by voting for all the others. In our example, most of those whose first preference was Conservative do exactly this, and since they don’t have a preference with the other parties they rank them according to the order in which they are listed. This is called a donkey vote and whilst it is most common where full preferential voting is required, it applies equally here. As a result the ‘second preferences’ for those who vote Conservative are divided 8,177 for Labour and 991 for the Liberal Democrats.

With the vote in, the count can begin, and after the first round the BNP, having the fewest votes, is eliminated. The next preferences of those votes are added to the remaining candidates to give us the following: just over 42% would like a Liberal Democrat MP with around 35% opting for Labour. It’s still not a majority so the Conservative vote is eliminated… and something interesting happens when the ‘second preferences’ are added to the count. These would be the people whose other preference was mostly ‘anyone but BNP’ and consequently voted for the other candidates in the order that they appeared.

Despite having significantly less of the ‘positive’ vote, Labour’s candidate wins through having a superior position in the alphabet.

As I stated previously, what this illustration and others show is how AV can work; the result – fair or otherwise – depends on how the example is framed. I could as easily have had the Conservative candidate prosper as a result of Labour’s anti-BNP sentiment; not perhaps to the extent of the numbers used above, but certainly enough to affect the outcome. This example doesn't say how likely it is, only that it’s possible; under AV you can have a result that many people would consider unfair; it’s a system not nearly as simple as some would have us believe.


  1. I take your point but it's telling that all the BNP voters go Conservative!
    Seriously though, the point is that the parties now realise that second preferences are important and so have to engage with people who are not necessarily their natural voters.

  2. I've found a major problem with this example.

    I wondered if it would be possible to have the order of the parties appear randomly - on different ballot papers. Then I thought - that might even be the way it is planned to be done. So I looked to see what an Australian ballot paper looks like. I found one here - http://blogs.abc.net.au/antonygreen/2011/03/what-does-an-australian-av-ballot-paper-look-like.html

    Check out this quote from the article featuring the image, "As you can see, the candidates are not listed in alphabetic order on the ballot paper. A random draw is held to determine order, appearing at the top of the ballot paper producing a minor advantage."

    So there you have it - sorry Phil! Maybe you can cook up an different one?

  3. @Pitch Twit - I'm aware of that, but if you think about it all that's missing from the example to cater for this is "after a random draw the candidates were ordered thus", and then the figures are re-jigged (or 'cooked up' if you prefer!) accordingly. I left this out to try and make it easier to follow.

    However, I believe Australia does have the answer to at least mitigate this - from what I've read they go one further (I don't know if this is in all states) and re-arrange candidates on different batches of ballot papers.

    Two points though: Which, if any, of these mitigating factors are we having in the UK?