[EM] Better Approval-voting option? Could ABucklin fail FBC?

Kevin Venzke stepjak at yahoo.fr
Thu Mar 1 18:06:24 PST 2012

Hi Mike,

De : MIKE OSSIPOFF <nkklrp at hotmail.com>
>À : election-methods at electorama.com 
>Envoyé le : Jeudi 1 mars 2012 15h55
>Objet : [EM] Better Approval-voting option? Could ABucklin fail FBC?
>But could this happen?:
>If you rank your favorite, F,  in 1st place, s/he gets a majority, even though s/he doesn't win, because someone else has a higher
>A number of people rank F, and, if you help F get a majority, then they won't give a vote to their next choice.
>That's regrettable, because their next choice could win with those votes, while F can't win. And when their next choice doesn't win,
>someone worse than s/he (as judged by you) wins.
>You got a worse result because you didn't favorite-bury.
>So maybe, even if that scenario is merely possible, I shouldn't propose Stepwise-to-Majority unless it turns out that the FBC-failure scenario
>can't happen.
>But more worrying is the fact that one could tell that same story about ABucklin (the ER-Bucklin defined at electowiki).
>Of course a vague verbal scenario like the above might not have an actual numerical example that can carry it out. There might
>be some reason why such an example couldn't work. Still, it's worrying.
>Does anyone know if there's actually a proof that ER-Bucklin meets FBC?  
>Can it be shown that the verbal FBC-Failure scenario described above couldn't really happen?
>Might ABucklin fail FBC?
I want to help but I'm not sure I understand the failure scenario you

With three candidates ER-Bucklin(whole) gives the same results as MCA.
There can't be much doubt that MCA satisfies FBC. But maybe you have in
mind a scenario with more than three candidates?
Off the top of my head I would argue that ERBW satisfies FBC because
when you raise your favorite to equal-top, this can only delay the
reception of votes for candidates that you like less than your top
candidates (because it's only on your own ballot that this has an 
effect). You aren't doing anything to delay acquisition of votes by
your top-ranked compromise choice from other voters.

Any thoughts?

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