[EM] Quick and Clean Burial Resistant Smith, compromise

[Kevin Venzke]

Hi Forest,

Le vendredi 7 janvier 2022, 18:28:06 UTC−6, Forest Simmons <forest.simmons21 at gmail.com> a écrit : 
> [Robert] opined ...
>
> "Probably Schulze or RP is the best thing to do for those cases when there is
> no Condorcet winner.  But getting that into legislative language is difficult,
> which is why I have advocated for BTR-STV."
> 
> Actually, neither RP nor Schulze has better Condorcet efficiency than
> Smith//TopTwoRunOff, which is the simple method you should be aiming for.

Of course the Condorcet efficiency is the same, however the compromise incentive
(or other incentives) won't be, across various methods.

What hurts my heart is if we will say "let's adopt Condorcet, so people don't
have to always vote for the lesser evil, and weak candidates won't spoil races,
etc." and then we leave so much of this promise on the table unused.

I just ran some 4-candidate 5-bloc no-ER random sims. I don't do exhaustive
searches so take these numbers as suggestive only (not even minimums/maximums).

Compromise incentive detected in what % of elections sans majority favorite:
3.0% best achieved by an experimental method
4.0% River, Schulze(WV), MAM
4.4% MinMax(WV)
4.6% BTP
10.2% MinMax(margins)
12.0% Bucklin
13.2% Condorcet//Approval (implicit)
14.6% FPCC (an extension of Stensholt BPW)
15.3% Condorcet//King of the Hill
17.2% TACC (implicit)
17.8% Condorcet//FPP
18.1% Condorcet//IRV and my extension of Kristofer's Linear method (tie)
18.3% BTR-IRV
26.5% IRV
40.4% FPP

To be fair, I am running the same ballots through every method, which may not
be realistic. These numbers can also differ if you generate scenarios based on
an underlying issue space. But aside from these points, I can't help but notice
that a lot of these "strategy-resistant" Condorcet methods are getting beat by
Bucklin.

Of course, Bucklin's Condorcet efficiency is really poor, and the truncation
incentive is horrendous. But what's the goal of Condorcet efficiency, is it an
end in itself? Personally I'm not comfortable thinking of it that way (maybe
because it's defined on the cast ballots only, which seems insufficiently
grounded in the underlying preferences which are what really matter).

I haven't tried to do an extensive study of the burial games possible under
Condorcet//FPP. But measuring similarity of results with three candidates, the
three most similar methods are BTR-IRV (literally the same method), Kristofer's
Linear method, and a bit further away, Condorcet//IRV.

I have a hunch that if you put your "strategy-resistant Condorcet" hat on and
evaluate C//FPP, you will find it to be "good."

Incidentally, if you want a Condorcet method where burial never looks attractive
in the first place (before even considering strategic responses to burial), the
best methods I have are Stensholt's (SV and BPW slash FPCC), C//IRV, and C//KOTH.
None are monotone though.

Kevin