[EM] IRV in action

[James Gilmour]

> James Gilmour had written:
> >But the thinking behind the use of the word in this context is also
> >instructive.
> >You have to remember that IRV is nothing more than a convenient method of
> >condensing an exhaustive ballot into one voting operation.  (It also
> >avoids all
> >the horse-trading that typically takes place between the successive rounds
> >of an
> >exhaustive ballot, but that's a different issue.)
>
Adam wrote:
> Some have argued that this "horse trading" allows compromise candidates to
> stave off defeat.

The problem with this "horse trading" is that the decisions are all made by the
parties and by the candidates, not by the voters.  With preferential ballots, the
voters decide.  Our problem is putting that into effect in an acceptable way
through the counting part of the voting system.


> >Whatever other defects it may have, IRV does ensure
> >that
> >the winner has the support of half or more of those who are voting at the
> >point
> >when the final decision is made.
>
> The winner does have "the support of half or more of those who are voting",
> but only over the remaining candidates.  You can't overstate the
> significance of that.  Good candidates, candidates who have more support by
> any reasonable measure, can be discarded by IRV before a final decision is
> made.

This is all true, but look VERY carefully at the words I actually wrote: "the
winner has the support of half or more of those who are voting at the point when
the final decision is made".   It is understood that IRV is an elimination system,
so any comment about the result assumes it is with regard to the state of
elimination when the winner achieved half or more of the available votes.

If some voters opt out part-way through by not marking all preferences (so that
their ballot papers become non-transferable), the eventual winner will still have
the support of half or more of those who are voting at the point when the final
decision is made.  Given the democratic right of voters to say "If it is a choice
among these other candidates, I have no further preference I wish to express", I
think that is a reasonable result.  And it is not a distortion of the truth.


>  Here's just such a "nightmare" example:
> 10% FarRight>Right>Centrist>Left>FarLeft
> 10% Right>FarRight>Centrist>Left>FarLeft
> 15% Right>Centrist>FarRight>Left>FarLeft
> 16% Centrist>Right>Left>FarRight>FarLeft
> 15% Centrist>Left>Right>FarLeft>FarRight
> 13% Left>Centrist>FarLeft>Right>FarRight
> 11% Left>FarLeft>Centrist>Right>FarRight
> 10% FarLeft>Left>Centrist>Right>FarRight
>
> "Centrist" has the most first place votes, the most second place votes, and
> the most third place votes.  Also, centrist is never ranked fourth or fifth
> on any ballot.  In any non-probabalistic election method except for IRV,
> centrist wins in a landslide.  But in IRV, centrist is eliminated in the
> third runoff, and Right beats left 51-49.
>
> The results won't usually be that blatantly undemocratic, of course, but
> the fact remains that the best candidate by most reasonable measures can be
> eliminated early in an IRV election.

I recognise the problem very well, but what is the practical solution?  I am very
sympathetic to Condorcet, but there must be serious questions about the public
acceptability of some of the results it is likely produce.


>  Claiming that the winner has majority
> support, without adding the caveat that that support only applies vis-a-vis
> the remaining candidates, deems like a distortion of the truth to me.

Not what I said - see above.

James