Does AV make some votes count more than others?

But, in many ways, your vote alone is not enough. In the days and weeks ahead, you also need to challenge your friends and colleagues who are thinking of voting “Yes”. Ask them why they are voting for it. I bet you none of their arguments will stack up – and you need to take them on.So when they say: “AV will make every vote count”, tell them it won’t. It will actually make some people’s votes -especially those who vote for extremist parties – get counted more than others. [David Cameron arguing against AV in the London Evening Standard].

Is the Prime Minister correct with this line of argument? I don’t believe so. A clue to the argument I’m about to advance that Cameron is incorrect lies in the fact that AV is also referred to Instant Runoff Voting.

In full (i.e. non instant) Runoff Voting, what happens is that if in the first round of voting, no candidate obtains a majority of the vote, the lowest placed candidate is eliminated and another round of voting occurs. This process repeats until a candidate obtains more than 50% of the vote.

AV/Instant Runoff Voting aims to approximate this process by replacing multiple rounds of voting with multiple rounds of counting. If you assume that voters who voted for a candidate in an earlier round will vote for the same candidate in later rounds unless that candidate is eliminated and that voters for eliminated candidates will redistribute votes according to their preferences, then by asking at the outset what those preferences are, and then performing multiple rounds of counting until a majority winner is found, you can eliminate the need for several rounds of voting but can still retain the essential point of Runoff Voting, namely trying to achieve majority support for the winner (admittedly the majority is only of those votes making it through to the final round).

Note that in full Runoff Voting, every voter gets a chance to vote in every round, and all votes count equally in each round of voting. By comparison, under AV, every voter gets a chance for their vote to count in each round (by stating their preferences should their preferred candidates get eliminated) and each vote counts equally in each round of counting, it’s just that some votes are first preference and some votes are later preferences, just as is the case under Runoff Voting.

Cameron’s argument implicitly ignores the fact that the votes obtained for a candidate on first preference in the first round get carried through to the next round unless and until that candidate is eliminated, which is the equivalent of voters sticking with the same candidate through multiple rounds in run-off voting. These votes are in fact counted once in each round just like every other vote is.

It thus seems to me that the argument Cameron advances is flawed, equivalent to claiming that full Runoff Voting makes the votes for the lowest placed candidates count more than higher placed candidates when it clearly doesn’t. Each round of voting/counting treats each vote equally under both systems.

The main thing missing from AV that you get in full Runoff Voting is actually the opportunity for voters to change their minds from round to round, i.e. vote for A in round one, but for B in round 2 despite A still being in the running. Runoff Voting thus allows voters to alter their preferences from round to round, but this opportunity is not available either in AV or FPTP, so is irrelevant to making a choice between AV and FPTP.


One Response to “Does AV make some votes count more than others?”

  1. lesley whitfield Says:

    This is exactly correct. I find it very hard to understand how David Cameron has got away with his argument being relatively unchallenged. I spoke to the electoral commission yesterday, who confirmed the point you make here, but said it was up to the YES campaign to say it.

    I guess I’m also pretty disappointed with the scientific/mathematical/academic community for not standing up and pointing this out – or maybe they just haven’t been heard?

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