Sunday, 16 January 2011

Problems with AV 2

This is a very quick one.
Should the candidate with the most support be elected? I think so.

Second part of the argument is slightly more complicated..but not by much.
What would you say has most support on average? A first or second preference?
If we agree, like I hope we can, that the higher the preference the higher the level of support, we can agree that counting all preferences the same does not accurately show support.

Who would you say has most support out of this example for instance?
Candidate A has 10 1st preference votes.
Candidate B has 5 1st preferences, 3 2nd preferences and 2 3rd preferences.
AV would say there is no difference between the two candidates.
Fptp would say that ' A ' wins

That is a simple one, what about the same example but with candidate B having an extra 4th preference vote.
How much more would you say a 1st preference shows support than a 3rd or 4th? Would it cancel it out perhaps?
Under AV ' B ' would be elected..

I don't think this reflects support at all.

1 comment:

  1. The easiest solution is to consider a head-to-head between just A and B. That's what First Past the Post was originally designed for anyway. That's where the name comes from. When there are only 2 candidates there is an actual post to pass, and it's at the 50% mark.

    If you want to see who's got the most support just run the two candidates against each other with no fringe candidates there to take votes away from other of them, and see who is preferred by the majority.

    In almost all situations (with the only exceptions being rare, mathematically fascinating but impractical cases that rely on voters voting counter-intuitively to satisfy the maths), the winner under AV would triumph.

    That's the real test of true support. AV would beat FPTP by FPTP's on standards of a head-to-head between the two.

    What it means is that a winner under FPTP who didn't get a majority, would only win because of the number of other candidates splitting the rival votes.

    Say you're the only left wing candidate, say a Green candidate, and you're up against a Conservative, a UKIP and a BNP. You live in a very right wing area, so you only get 28% of the vote. However the rest of the votes are all split pretty evenly. 22% BNP, 24% UKIP and 26% Conservative.

    So the Greens win under FPTP, but hardly convincingly, and it's highly likely that you'd lose a head to head against ANY of the other three far more right-win candidates. Assuming no-one voted tactically here (if they had, chances are the Conservative candidate would have won), the fact that the Green got more first preference votes than either of the others is no justification for the victory.