[EM] A problem with IRV3/AV3 (Jameson Quinn)

David L Wetzell wetzelld at gmail.com
Mon Jan 9 12:28:53 PST 2012

> ---------- Forwarded message ----------
> From: Jameson Quinn <jameson.quinn at gmail.com>
> To: EM <election-methods at lists.electorama.com>
> Cc:
> Date: Sun, 8 Jan 2012 19:03:29 -0600
> Subject: [EM] A problem with IRV3/AV3
> Imagine a scenario of an ABCD one-dimensional continuum:
> 41: A>B>C
> 19: B>A>C
> 20: B>C>D
> 20: C>B>D
> If the A voters vote A>>D then A will win. By raising the turkey D over
> the true CW B, they have stolen the win. Even if their strategy fails to
> keep B out of the top 3, they lose nothing; B will still win.

thanks for doing this.  In the first stage wouldn't B and C tie for 3rd
place if only the first set of voters all voted strategically together in
the same way?     They'd both get rankings from 59 of the voters.  So if it
came down to a coin-toss, there'd be a 50-50 chance of the CW winning vs
the 2nd place candidate given a massive coordinated strategic vote by only
a subset of the sample (We assume none of the 3rd or 4th set of voters
decide to strategically leave off D rankings)?

> To be honest, it was harder to tune this scenario than I thought it would
> be. Thus, having taken the time to write this down, I am no longer opposed
> to IRV3/AV3. (For IRV2/AV2, it's easier to get this problem. It's also
> easier to get the problem if there are clones involved, but real-world
> clones beyond 3 candidates are unlikely.)

Thank you again.

The MSM+relevant portion of the Blogosphere shd be helpful in identifying
clones in real world.

> Since I'm now not opposed to IRV3/AV3, I consider it one of the 3 reforms
> (along with SODA and IRV) that would be most acceptable to incumbents,
> because it avoids the weak Condorcet winner problem.

remind me what is the weak Condorcet winner problem?

> Still, it is basically just as bad as IRV for nonmonotonicity and
> spoilers; all the spoiler scenarios I consider realistic are essentially
> 3-candidate anyway. As such, I see no reason to believe that it would not
> lead to lesser-evil voting and 2-party domination, as IRV does. Since I see
> 2-party domination (as opposed to just having 2 strongest parties, a
> logical necessity) as a source of the most-serious problems with Plurality,
> I still feel that SODA is a much better option than IRV3/AV3.

dlw: And our difference is that I see the near exclusive use of Plurality
voting rules as the source of my country's current evils, since it's not
hard to imagine 2 party dominated system that is a lot better.  All it
takes is for there to be better checks and balances between them and for
there to be two quite different major parties plus scope for
outsiders/dissenters to express themselves via minor parties and LTPs.

ps, I'm going to repost this on my blog.

> Jameson
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