[EM] I need an example of Condorcet method being subjected to the spoiler effect if any

[Kathy Dopp]

Thanks Kristofer for the explanations.  Do you know a good place that
discusses the Ranked Pairs method of resolving cycles, or all the
methods of resolving cycles?  I would still like an example of  a
spoiler in Condorcet no matter how unlikely if possible.  Thank you.

Kathy

On Thu, Jan 21, 2010 at 2:29 AM, Kristofer Munsterhjelm
<km-elmet at broadpark.no> wrote:
> robert bristow-johnson wrote:
>>
>> i think that the answer is "no", if a Condorcet winner exists and that all
>> bets are off if a CW does not exist, except, perhaps for these
>> "strategy-resistant" methods such as Markus Schulze's method.  i sorta
>> understand it, but since he hangs here, i think Markus should address the
>> question if the Schulze method is spoiler free.
>
> MAM/Ranked Pairs is also pretty strategy-resistant and is easier to
> understand. Schulze has the advantage of producing better results in some
> cases (closer to Minmax), but if "ability to describe to the public" is
> important, then Ranked Pairs wins there.
>
>>> Could someone please provide me with an example of the spoiler effect
>>> occuring with the Condorcet method  of counting rank choice ballots or tell
>>> me why the spoiler effect doesn't happen with Condorcet in  a few words?
>
> (...)
>
>> i would say that (with the CW existing), it's spoiler-proof.
>
> Yes. If there's a CW and a candidate is added, and that candidate doesn't
> create a cycle, then the winner doesn't change. All the "tricky" stuff
> happens when there is a cycle, or the candidate makes one.
>
> The advanced methods can claim further resistance: Schulze and Ranked Pairs
> both make their winner decision independent of candidates not in the Smith
> set. River is independent of Pareto-dominated alternatives - a candidate is
> Pareto-dominated if everybody who ranks both him and some other (specific)
> candidate, rank the other candidate above him (e.g. X is Pareto-dominated by
> Y if all voters who rank both X and Y say Y>X, and there's at least one such
> voter).
>
> I imagine these resistances would mostly come into play in smaller
> elections. Still, they're nice to have, and their existence immediately
> tells parties not to try exploiting certain weaknesses (because it won't
> work).
>



-- 

Kathy Dopp

Town of Colonie, NY 12304
phone 518-952-4030
cell 518-505-0220

http://utahcountvotes.org
http://electionmathematics.org
http://kathydopp.com/serendipity/

Realities Mar Instant Runoff Voting
http://electionmathematics.org/ucvAnalysis/US/RCV-IRV/InstantRunoffVotingFlaws.pdf

Voters Have Reason to Worry
http://utahcountvotes.org/UT/UtahCountVotes-ThadHall-Response.pdf

Checking election outcome accuracy --- Post-election audit sampling
http://electionmathematics.org/em-audits/US/PEAuditSamplingMethods.pdf