Very good example. Thanks.
On Fri, Sep 23, 2011 at 4:32 PM, Toby Pereira <[email protected]> wrote: > Andy > > Candidates can go up the rankings or down when a candidate is eliminated in > IRV, and it's possible to do both in different rounds. A plurality winner > could slip down and be eliminated in a case where they would have still gone > up again and won had they not been eliminated. So: > > 30: A>B>C>D > 26: B>A>C>D > 24: C>A>B>D > 10: D>B>A>C > 10: D>C>A>B > > Round 1: > A: 30 > B: 26 > C: 24 > D: 20 > > D eliminated > > Round 2: > B: 36 > C: 34 > A: 30 > > A eliminated > > Round 3: > B: 66 > C: 34 > > B wins the IRV election whereas A would have been the plurality winner > and the (quite strong) Condorcet winner. > > A>B: 64-36 > A>C: 66-34 > A>D: 80-20 > > Toby > > > *From:* Andy Jennings <[email protected]> > *To:* EM <[email protected]> > *Sent:* Saturday, 24 September 2011, 0:13 > *Subject:* [EM] Is there any profile where IRV is worse than Plurality? > > Since we're discussing IRV quite a bit lately, here's a question: > > - Is there any voter profile where IRV gives a worse result than plurality? > > I can't seem to think of one. So is it true that, mathematically, IRV > dominates Plurality, that is IRV is always at least as good as plurality and > sometimes strictly better? > > > Even if that is true, I still believe that IRV is harmful, socially. By > successfully avoiding the traditional spoiler problem (where spoilers are > very weak), it leads people to believe that it is immune to the spoiler > problem. Then it leads them directly into the second-tier spoiler scenarios > where a large group of voters will, by voting honestly, cause their least > favorite candidate to win. > > ~ Andy > > ---- >
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