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

robert bristow-johnson rbj at audioimagination.com
Sun Jan 22 01:08:11 PST 2023

> On 21.01.2023 20:49, robert bristow-johnson wrote:
> > Here is my question: Suppose that cycles *never* happened.  Suppose
> > we were somehow guaranteed that there is *always* a Condorcet winner.
> > And also suppose we're far enough from a cycle that no collective
> > strategy would succeed at pushing the election into a cycle.  Then,
> > *if* there is always a CW, is there any strategy that will serve a
> > voter's political interest  than better than ranking the candidates
> > sincerely?

On 01/21/2023 5:18 PM EST Kristofer Munsterhjelm <km_elmet at t-online.de> wrote:
> If there is a CW, then IIA always holds, yes. Suppose X is the CW and Y 
> is someone else. Then running the election without Y doesn't change 
> anything: X still beats everybody else pairwise and wins.
> Thus if somehow you could prevent both sincere and tactical Condorcet 
> cycles, the method would be strategy-proof. (Strictly speaking, this 
> doesn't invalidate Arrow's theorem because a method that magically 
> forbids Condorcet cycles would fail universal domain.)

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.  It's as effective at suppressing the spoiler effect as it is effective at electing the Condorcet winner.  FairVote has to credit any success they claim for IRV to Condorcet.  Because when IRV fails to elect the CW, it doesn't do shit about preventing the spoiler effect and all the pathologies cascading from that failure to prevent the election from being spoiled.

And I do consider that 0.4% of the time a CW exists and is not elected to be simply a failure of Hare RCV to do what it promises to do, when correcting that (by making the RCV method Condorcet-consistent), can only be a beneficial thing.

> > 
> > We know that Condorcet cycles can occur and in the U.S. there is one
> > known RCV election that demonstrated a cycle, the 2021 Minneapolis Ward
> > 2 City Council election.  It was a simple Rock-Paper-Scissors cycle;
> > Smith set of 3.
> > 
> > I think it's the case that we know that the necessary ingredients
> > for  a cycle is a very close 3-way race *and* that there is at least a
> > 2-dimensional political spectrum (Nolan chart) with candidates and
> > voters spread out all over the map in 2 dimensions, *not* in mostly a
> > linear spatial distribution.  There has to be a sorta political
> > schizophrenia where a lotta voters are saying something like "If I can't
> > have my favorite, Bernie, then I'm voting for T****."
> There could also be simple noise, i.e. some candidates are extremely 
> close, the voters randomly fill in what's really equal-rank, and the 
> random fill happens to create a Condorcet cycle.
> IIRC, Worlobah and Arab were very close in the Minneapolis election, so 
> the cycle could be a result of noise, but I don't know the circumstances 
> well enough to say for sure.
> On 01/21/2023 7:42 PM EST KenB <kdbearman at gmail.com> wrote:
> = = = = =
> [KB]  That's correct.  There was very little difference in political 
> positions among most of the Ward 2 candidates.  I didn't pay close 
> attention to their specific positions because I live in a different ward.
>    - Ken Bearman, Minneapolis MN

I actually have family living in Minneapolis, but have no idea of what ward they are in or where they are regarding city politics.  But that you're there, Ken, is very interesting.  I wonder if the candidates themselves understand the unique situation the were in.


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

"Imagination is more important than knowledge."


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