[EM] Suppose, for a moment, there were never any cycles...

robert bristow-johnson rbj at audioimagination.com
Sun Jan 22 19:37:23 PST 2023

I wrote:
> > 
> > Well I don't really expect to prevent cycles, but just by doing nothing, I can plan on them
> > being extremely rare, 0.2% of the time.  So it's a faux-suppression of cycles, a
> > pseudo-effect.  Either way, I can say that the reason that IRV is good at avoiding the
> > spoiler effect is solely because 99.4% of the time IRV elects the Condorcet winner.
> > 

> On 01/22/2023 9:08 AM EST Kevin Venzke <stepjak at yahoo.fr> wrote:
> That sounds to me like a pretty big concession.

We gotta be honest with the facts.  I don't consider it a concession.

> To the extent a method deals badly with spoilers, the interested parties will aim to avoid
> the issue through their nomination choices or voting advice.

I doubt it.  I doubt that, on the local, state, or national level, anyone will be looking at this to strategically nominate candidates that somehow will prevail if FPTP fails to get a majority or if IRV fails to elect the CW or if a Condorcet method has to deal with a cycle.  I predict zero nominations will be materially affected by such considerations.

But if a failure happens, people will notice.  And there will be a loss of trust in the system and the elected candidate *may* very well suffer from a perception of diminished legitimacy.

> For example FPP always elects the CW on those ballots.

Oh, that seems to me to be a little disingenuous.  There's only one ranking level other than unranked.  You don't know who the CW is if voters were allowed to be more specific about their preferences.  It's like the Approval folks insisting that their better at electing the CW than IRV.

> Spoiled FPP elections aren't that common.

No.  But they do happen and people remember.  BTW, for FPTP we don't know for sure they *are* spoiled because, without the ranked ballot, we don't know for sure who voters for the ostensible spoiler would have voted for had that candidate not run (or if there was a ranked ballot).

In Vermont we remember two fairly recent high-profile races that were *likely* spoiled: the 2014 gubernatorial election and the 2021 Burlington mayoral election.  But to know if they really were spoiled, we would need more information that only a ranked ballot gives us.

> But we would probably say that's because they tried not to have 3+ candidates on
> the ballot, not because FPP is so Condorcet-efficient.

"They" are who?  Each party only nominates a number of candidates equal to the winning seats.  Independents (and those signing their petition to get on the ballot) choose independently if they're gonna run or not.

> I can't say with any certainty how different the nomination incentives under IRV are in
> comparison to any specific Condorcet method, but they shouldn't be the exact same.

I think, without additional information, we have to assume they're the same.  It's similar to people telling me that people would mark their ranked ballot differently if they knew it was which Condorcet method or IRV.

> One
> obvious element is that a would-be IRV candidate expecting few first preferences is
> probably not viable, and so might choose not to run for that reason.

Well "few" is both a qualitative and quantitative term.  The extreme hypothetical that IRV apologists like to toss at me is the milktoast candidate that is everyone's 2nd-choice and no one's first.  Now how does Candidate Milktoast become the CW.  The extreme they toss out is:

 500   Left > Milktoast > Right
 500   Right > Milktoast > Left
   1   Milktoast > either Left or Right > the other one

It's a highly polarized and evenly split electorate. Now, even with only 1001 ballots, how likely is that going to happen?  It's astronomically low.

Now it get's less astronomical.  Assuming 3 significant candidates (all making it to the semifinal round), an IRV election that fails to elect the CW will fail because of the Center Squeeze effect.  That is the seminal flaw.  Now, what are the odds of that happening?  Astronomically low?  Or just very low?  And that centrist candidate will have a lot of first-choice votes from voters, just less than the other two.

So I consider the Candidate Milktoast argument to be a red herring.  In Burlington 2009, Andy Montroll was the centrist candidate but he's not milktoast.  I presume the same is true for Nick Begich in Alaska.

> I hope Condorcet
> incentives are noticeably different in this sort of vein. Otherwise this statement above
> seems to tell me that IRV is 99.4% right already, that all we can do is fix the 0.6%, and
> that seems a little demotivating to me.

Well, we can only fix 0.4%.  Condorcet, Arrow, Gibbard, and Satterthwaite tell us that the other 0.2% can't be fixed.  (But we can do the best we can in that one election out of more than 500.)

While this avoidable failure happened only twice (that we know of in the United States), it can happen again. Occasionally we read about surgeons accidentally amputating the wrong limb because of a procedural mixup. When this happens, do we hear hospital officials defending their procedures saying "These procedures have served us well for decades and hundreds of surgeries, so we see no need to change our procedure at all"?

No. Even with a single catastrophic mistake, that is enough to motivate review and make changes in procedure to insure that such an unnecessary failure will not happen again. Now is precisely the time to recognize this failure that occurred in Burlington in 2009 and in Alaska in August 2022.

Suppose you were going to have life-preserving surgery and had a choice of two different surgical procedures, one that has a 0.6% table mortality and the other with 0.2%.  All other things equal, which treatment would you choose?

Elections are about majorities.  If we do not elect the majority candidate, then the votes coming from the voters supporting the minority-favored winning candidate had votes that had more juice, that counted more, than those votes from the greater number of voters supporting the majority candidate.  Elections that elect the wrong candidate are failed elections.  Fucking up an election is a big deal.  Something to be avoided whenever we can possibly avoid it.


r b-j . _ . _ . _ . _ rbj at audioimagination.com

"Imagination is more important than knowledge."


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