[EM] halp!

robert bristow-johnson rbj at audioimagination.com
Thu Aug 5 19:07:07 PDT 2021

thanks for doing this.  i might email you directly if i need help decoding it.

> On 08/05/2021 10:32 AM Kristofer Munsterhjelm <km_elmet at t-online.de> wrote:
> On 05.08.2021 03:08, robert bristow-johnson wrote:
> > i just got offa the phone with a Dr. Tideman.  you guys might know him.  could someone here, who is more qualified than me, put in a new line into this table at Wikipedia:
> > 
> > https://en.wikipedia.org/wiki/Comparison_of_electoral_systems#Compliance_of_selected_single-winner_methods 
> > 
> > for BTR-STV ?   https://electowiki.org/wiki/Bottom-Two-Runoff_IRV
> > 
> > I know that BTR is Condorcet-compliant (which means that it cannot be LNH) and that, strictly, it's not precinct summable (if there was a cycle, you don't know from the summable defeat data who wins).  But I am not qualified to get the facts and authoritatively evaluate each criterion and say "yea" or "nay" to it.
> > 
> > geez, i can't pay you, but i can beg.
> This is what I know:
> Every monotonicity property IRV fails, BTR-STV/BTR-IRV also fails.
> Majority, Condorcet: pass (obviously; all implied by Condorcet)
> Smith, Mutual majority, majority loser, Condorcet loser: pass (Smith
> implies the rest)
> Clone independence: fail (crowding: https://www.rangevoting.org/BtrIrv.html)
> IIA: fail
> Reversal symmetry: fail (because IRV fails it)
> Consistency: fail (winner consistency incompatible with Condorcet, and
> no Condorcet method but Kemeny passes social order consistency)
> Participation, favorite betrayal: fail (incompatible with Condorcet)
> Later-no-help, later-no-harm: fail (ditto)
> Polynomial runtime: O(n^2)
> Summable: O(n!)
> Resolvability (Woodall's version): pass if the elimination count breaks
> ties by second preference (then third, fourth, etc), otherwise I don't know.
> Also (not mentioned on the list):
> Plurality: pass
> Mono-add-top: fail (incompatible with having both Smith and Plurality)
> These I'm not 100% certain about:
> LIIA: Pretty sure this is a fail, though I could be wrong.
> ISDA: Not sure, but I would expect fail.
> So all we need to do is to find a LIIA failure and an ISDA failure.
> Anyone got such failures?
> I'm kinda thinking I should make a simple Python program "How Your
> Method Sucks" that finds criterion failures.
> I kid :-) About the title, at least. It *would* be nice to just throw a
> method at some program and get "definitely fails these".
> -km


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

"Imagination is more important than knowledge."


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