[EM] Why I think IRV isn't a serious alternative 2

[Kevin Venzke]

Hello,

--- En date de : Dim 21.12.08, Abd ul-Rahman Lomax <abd at lomaxdesign.com> a écrit :
> > Hello,
> > 
> > --- En date de : Ven 19.12.08, Abd ul-Rahman Lomax
> <abd at lomaxdesign.com> a écrit :
> > 
> > > With LNH, the "harm" is that the voter
> sees a
> > > second preference candidate elected rather than
> the first
> > > preference.
> > 
> > Actually, the harm need not take that form. It could
> be that you add an
> > additional preference and cause an even worse
> candidate to win instead of
> > your favorite candidate.
> 
> That's not called LNH, I think. LNH: Adding an
> additional preference cannot cause a higher preference
> candidate to lose.

I didn't contradict that. I contradicted the statement quoted. When a
voter adds a preference and so makes a preferred candidate lose, there
is no guarantee that the new winner was ranked by this voter, according
to the definition of LNHarm.

> With Bucklin, the described behavior can't occur, if
> I'm correct.

That's correct.

> > Yes, but the concern should not be that you personally
> will ruin the
> > result, it's that you and voters of like mind and
> strategy will ruin the
> > result.
> 
> There are two approaches: true utility for various vote
> patterns, which is the "last voter" utility, since
> if your vote doesn't affect the outcome, it has no
> utility (except personal satisfaction, which should, in
> fact, be in the models. There is a satisfaction in voting
> sincerely, all by itself, and this has been neglected in
> models.)
> 
> The other approach is the "what if many think like
> me?" approach. That's not been modeled, to my
> knowledge, but it's what I'm suggesting as an
> *element* in zero-knowledge strategy. It's particularly
> important with Approval! The "mediocre" results in
> some Approval examples proposed come from voters not
> trusting that their own opinions will find agreement from
> other voters, and if almost everyone votes that way, we get
> a mediocre result. This actually requires a preposterously
> ignorant electorate, using a bad strategy.

That's not very relevant to the point I was making. I was saying it
doesn't matter whether a given (negative) change to the outcome can
be achieved by a single voter, or whether it takes a group of like-minded
voters.

> From the beginning, we should have questioned the tendency
> to believe that "strategic voting" was a Bad
> Thing.

All things being equal it is a bad thing, when the alternative is
sincerity. There are situations where it helps, is all.

> > > I'd have to look at it. How does MMPO work? I
> worry
> > > about "nearly," [...]
> > The "opposition" of candidate A to candidate
> B is the number of voters
> > ranking A above B. (There are no pairwise contests as
> such, though the
> > same data is collected as though there were.)
> > 
> > Score each candidate as the greatest opposition they
> receive from another
> > candidate.
> > 
> > Elect the candidate with the lowest score.
> > 
> > This satisfies LNHarm because by adding another
> preference, the only
> > change you can make is that a worse candidate is
> defeated.
> 
> Okay, that's clear. Now, "nearly" a Condorcet
> method?

If truncation and equal ranking are disallowed then it is a Condorcet
method (and equivalent to the other minmax methods). Discrepancies
occur when equal ranking and truncation are allowed, because instead of
candidates only being scored according to contests that they actually
lose, they are scored according to all of them, even the ones they win.

> But this is a peripheral issue for me. Reading about
> MMPO, my conclusion is that, absent far better explanations
> of the method and its implications than what I found
> looking, it's not possible as an alternative. 

But that's irrelevant. I'm not trying to persuade you to advocate MMPO.
I'm pointing out again that you can't effectively criticize LNHarm by
using arguments that are specific to IRV.

> > DSC is harder to explain. Basically the method is
> trying to identify the
> > largest "coalitions" of voters that prefer a
> given set of candidates to
> > the others. The coalitions are ranked and evaluated in
> turn. By adding
> > another preference, you can get lumped in with a
> coalition that you
> > hadn't been. (Namely, the coalition that prefers
> all the candidates that
> > you ranked, in some order, to all the others.) But
> this doesn't help
> > the added candidate win if a different candidate
> supported by this
> > coalition was already winning.
> 
> MMPO is easy to explain, but the *implications* aren't
> easy without quite a bit of study. DSC being harder to
> explain makes the implications even more obscure. Thanks for
> explaining, I appreciate the effort; but I'm
> prioritizing my time. I'll need to drop this particular
> discussion. If, however, a serious proposal is made for
> implementing one of these methods, I'll return. 

Again, the point was not to encourage you to advocate DSC.

Kevin Venzke