[EM] IRV in action

[James Gilmour]

> James Gilmour wrote:
> >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.

Adam replied
> I wasn't really referring to the horse trading at the party level - rather
> I was referring to the chance voters have to evaluate the support
> candidates have, and decide if they should dump their top surviving choice
> in favor of a compromise candidate.  I'm not claiming I think this is a big
> factor; I'm only saying that some people have mentioned it as a possibility.
>
Adam had written earlier:
> > > 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.
> >
James said:
> >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.
> >
Adam replied:
> I'm not really concerned with the attrition of the voters; I'm more
> concerned with the attrition of the candidates.  That "support" could
> consist mostly of voters choosing their second least favorite over their
> least favorite.

The most important people in any election are the voters.  Candidates and parties
may be important, but they are less important than the voters.  Maybe we can do
better than offer voters choosing their second least favourite over their least
favourite, but even that would be an immense improvement over what we've got right
now.


> > >  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-probabilistic 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.
>
> I suppose the "nightmare" scenario for Condorcet (in your mind) looks
> something like this:
>
> 47% Right>Centrist>Left
> 5% Centrist>Right>Left
> 5% Centrist>Left>Right
> 43% Left>Centrist>Right
>
> So a candidate with only 10% first place support wins, over two candidates
> with over 40% first place support each.  A couple thoughts here:
>
> 1)  I think it's hard to argue this is _worse_ than the IRV nightmare
> example above.  Even the layman can recognize that centrist was a
> compromise choice.
>
> 2)  After the election results are announced, nobody has any reason to
> regret their first place vote.  The same is not true in IRV, in the case
> above and in many others.  Winning votes Condorcet, in general, minimizes
> the tendency to regret your vote.
>
> 3)  If we're just talking about the public perception of a Condorcet result
> like the above one, then you can take Forest Simmons' advice and use a
> graded ballot.  It's hard to argue viscerally against the candidate that
> got mostly B's and a few A's, when the other candidates got a mix of A's
> and C's.

What you say makes good sense theoretically and for the examples you present, but
I'll take this issue further in a separate post.

James