Wednesday, April 20, 2011

Why I am voting Yes to Alternative Vote

On May 5th the UK votes whether to change its electoral system from "first past the post" (FPTP) to "alternative vote" (AV). In FPTP you put an X next to the name of one candidate, and the candidate with the biggest number of Xs wins. In AV the first preferences are counted as for FPTP, but then the candidate with the lowest number of votes is eliminated and the second preferences of their voters are then counted towards the other candidates. This process carries on until someone has more than 50% of the vote.

When I was at University the Students Union used AV, and one year a man stood for the post of Womens' Officer under the name of "Captain Kirk". Against him were two more conventional candidates standing on the Conservative and Labour platforms.

When the votes were counted Captain Kirk got 49% of the first preference votes, with the Conservative getting 26% and Labour 25%. Under FPTP Kirk would have won, but now the Labour candidate was eliminated and it turned out that all of the people who voted for her first had voted for the other woman as second preference. So now the Conservative candidate had 26%+25%=51% of the vote, and Kirk was defeated.

I'm well aware of the Arrow Impossibility Theorem, which shows that given an election with three or more candidates and three or more voters it is impossible to have a voting system that always delivers the right result, but it seems to me that this is rather like the fact that any programming language is logically equivalent to a Turing Machine; its true, but it doesn't mean that all (voting systems | programming languages) are equally good. FPTP seems particularly prone to perverse outcomes, such as the election of a male Womens' Officer when the majority of the electorate wants a female. Pretty much every election in the UK is a 2-horse-1-pony race, with the Liberal Democrats as the pony, and every election pundits discuss the impact of "tactical voting" as people who would like to elect the Lib Dems instead vote Labour for fear of otherwise "letting the Conservatives in". Under AV they can simply vote Lib Dem first and Labour second.

The anti-AV campaign's arguments seem to come down to:
  • It will create more hung parliaments. Possibly. I don't see this as a bad thing. The current coalition seems to be doing OK, and a coalition means that more of the electorate's views get represented in government. Having a government elected by 40% of the people get 100% of the power seems to me rather undemocratic.
  • It will empower the National Front. For those who don't know, the National Front (NF) is an extreme right wing racist party, which occasionally does well in poor inner-city areas where the "immigrants are taking your jobs and houses" line gets a sympathetic hearing. But equally, if most people object to the NF on principle then AV makes it much easier to vote against them; just put the NF at the bottom of your list. That ensures that no matter how other people vote, your vote will count against the NF.
  • The most popular person doesn't always win. Well yes, if you define "most popular" as "winner under FPTP" then this is true; if AV didn't give a different result sometimes then there wouldn't be any difference. The point about AV is that the candidates with the broadest support tend to win much more often, whereas FPTP is prone to producing winners who most of the electorate actively dislike.
So for these reasons I'm going to be voting YES to AV.

3 comments:

Luke Plant said...

I'll try again, my first attempt was rather rubbish.

You write: "just put the NF at the bottom of your list. That ensures that no matter how other people vote, your vote will count against the NF."

The problem is, this isn't really true.

In the first round, only the first preference votes are counted.

If you vote for the most popular candidate, the order of your votes for other candidates are not relevant, because only those ballot papers for the eliminated candidates get re-examined after the first round.

Suppose the procedure comes to a conclusion after the second. The fact that you put one candidate 2 and another 5 has not influenced the vote at all.

This means that if you happen to prefer the more popular candidates, your preferences against the other candidates are not counted, but if you prefer the least popular candidates, your other preferences are counted.

As you say, no voting system is fair, but AV is biased towards the minority opinions.

This is why many people think that it is AV, not FPTP, that produces the perverse results.

Paul Johnson said...

Luke,

In your example, the only reason that the vote doesn't count against the NF is that they've already lost, so its irrelevant.

"Bias" is a loaded term; it seems to me that FPTP is biased towards the big parties. The Lib Dems need far more votes to get an MP than either the Conservatives or Labour.

Gabriel said...

With AV, you need to rank candidates on a single ballot: this is prone to the ballot-as-signature attack (coercing someone's vote).

http://hal.archives-ouvertes.fr/hal-00142440