[EM] IRV vs RCV

[C.Benham]

>   i think that Schulze is likely the most resistant to voting strategy, but it's too difficult to explain to legislators and the public.
> Yeah, I agree.  I'm willing to take it on faith that BTR-STV is more
> susceptible to strategy than methods that guarantee Smith set
> membership, but I suspect that Condorcet-compliant methods perform
> better at strategy resistance than standard IRV does.
>
>
How does BTR-STV not "guarantee Smith set membership" ?      It is a 
silly Mickey Mouse method that (at least) pointlessly fails Clone 
Independence.

Why do you (Rob)  suspect that all "Condorcet-compliant methods perform 
better at strategy resistance than standard IRV does"?

IRV is somewhat more vulnerable to Compromise than Condorcet methods at 
the expense of being much more vulnerable to Burial strategy.

43: A
03: A>B
44: B>C (sincere is B or B>A)
10: C

Here A is the sincere and voted  FPP and IRV winner and the sincere 
CW.   C is a should-be-irrelevant (say) extreme wing candidate.

Schulze, Ranked Pairs, MinMax, Smith//MinMax using Winning Votes (as 
Schulze himself advocates) or Margins (as Robert advocates) as the measure
of defeat-strength all reward the insincere voters (who simply Buried 
against the other front-runner, nothing implausibly ingenious) by 
electing B.

I rate plain IRV  (where the voters are free to strictly rank from the 
top as many candidates as they like and eliminations are one-at-a-time) 
as better
than the worst Condorcet methods such as Margins and  "BTR-STV".

Chris  Benham

On 17/12/2019 5:42 pm, Rob Lanphier wrote:
> On Sat, Dec 14, 2019 at 7:21 AM robert bristow-johnson
> <rbj at audioimagination.com> wrote:
>>> On December 14, 2019 2:44 AM Rob Lanphier <robla at robla.net> wrote:
>>> I also like Ranked Pairs, but
>>> I suspect that all of the methods that pick a candidate out of the
>>> Smith set are indistinguishable in real-world conditions.  My hunch is
>>> that an analysis of the public elections that had ranked ballots would
>>> reveal that all of them had a single Condorcet winner,
>> except, of course, Burlington Vermont 2009.
> I'm pretty sure all of the Condorcet-winner compliant methods chose
> Andy Montroll, given the ballots from the Burlington 2009 election.
> Copeland, Schulze, Ranked Pairs,  etc.  Was there a discrepency
> between Condorcet methods, or just the well-documented discrepency
> between the Condorcet methods and IRV?
>
>>> and therefore
>>> there would be no difference between the results of Ranked Pairs,
>>> Schulze, Tideman, Schulze, or even Copeland.
>> this is the difficult point i have tried to say here.  i think that Schulze is likely the most resistant to voting strategy, but it's too difficult to explain to legislators and the public.
> Yeah, I agree.  I'm willing to take it on faith that BTR-STV is more
> susceptible to strategy than methods that guarantee Smith set
> membership, but I suspect that Condorcet-compliant methods perform
> better at strategy resistance than standard IRV does.
>
>
>> BTR-STV is different.  Schulze, RP, MinMax (dunno about Copeland) all elect the same candidate in the case of an CW or a Smith set of 3.  i don't ever ever ever expect to see a Condorcet RCV ever have a Smith set larger than and i really don't expect to see one without a CW.
> Copeland isn't guaranteed to pick a candidate out of the Smith set
> when the Smith set is bigger than one, so it's possible it'll pick a
> different winner than Schulze, RP, MinMax, etc when the Smith set is
> 3.
>
>>>   So BTR-STV seems like a
>>> fine compromise, since IRV has failed to pick the Condorcet winner in
>>> at least one recent public election.
>> yes, and i am trying to remind the Progs of that.  but they are not listening.
> *sigh*.  Yeah, sounds tough.  We had a close mayoral election here in
> San Francisco in 2018.  Given how close it was, I was really terrified
> that we'd end up with an election like Burlington 2009.  Thankfully,
> the IRV elimination order didn't threaten to eliminate the Condorcet
> winner.  The closeness of the race was between two candidates who
> probably would have been the final two candidates in a BTR-IRV tally
> (though the third place candidate wasn't far behind either of the
> frontrunners).  Given the closeness bitterness of the race, it would
> have been an electoral reform disaster if any of the top three
> candidates had lost the way that Andy Montroll did in Burlington (as
> the Condorcet winner and IRV loser).
>
> Rob
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