A thought on:
> From: Mike Ositoff <[EMAIL PROTECTED]>
> Subject: Runoff vs IRO
> Let me re-copy the example I posted before, where IRO fails
> badly but Runoff doesn't:
>
> 60 70 100 83 75
> A B C D E
> B D
My 'normal' model of voting is a text-book 1-D spatial one, with
issues from left to right. In Mike's example I imagine that parties B
and D would tend to move their posture towards C to increase their
share of the vote. C could not defend against this, and so would get
'squeezed out'. I certainly couldn't fit UK parties to this model. I
would expect A and E to move 'in' too.
> When the candidate support tapers toward the extremes, as
> it will be if the voters are distributed normally (in both
> senses of the word), and when the smaller outer candidates
> are still big enough to tip the scales among the inner candidates
> when their transfers go inward after elimination, then
> IRO will screw up in this way every time.
But how common is this? Downs has an economic theory of voting, in
which candidates/parties attempt to maximize their support. Does this
only apply to the UK?
> If elimination starts near the middle, and the biggest candidates
> are more extreme, than in that special situation it's possible
> to contrive an example where IRO elects a CW but Runoff doesn't.
Not contrived - look at the UK!
> It's necessary to have a candidate next to the CW who is
> even smaller than the CW, who at the start gives his transfers
> to the CW.
We have single-issue parties from time to time (eg., the Greens) and
plenty of independents who fit this description.
>Runoff fails to elect the CW in that example because
> the biggest 2 candidates are extremes:
><SNIP>
>
> This is, by comparison, a special trick example, which
> makes IRO do better than Runoff at electing a CW.
In the UK, the biggest parties are often extremes. No trick!
> 4. IRO, but not Runoff, can fail to elect a CW who is everyone's
> exclusive 1st or 2nd choice.
(Since corrected by Mike))
> Runoff is better than IRO. Regrettably IRO is being proposed
> in some communities to replace Runoff.
>
> No on Measure F in Santa Clara.
Santa Clara is not like the UK! Maybe there is no universal best
method. Just a universally worst one: FPP!
--------------------------------------------------
Sorry, but apparently I have to do this. :-(
The views expressed above are entirely those of the writer
and do not represent the views, policy or understanding of
any other person or official body.
