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

[Jameson Quinn]

2012/1/9 David L Wetzell <wetzelld at gmail.com>

> ---------- 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?
>
Right, though of course it would be easy to fix that by changing some
fraction of the B>A>C voters to B>A.


>     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?
>

A polarized electorate, 49% A, 49%B. 2% support an unknown centrist X. Now,
25% each from A and B decide, "X couldn't possibly be worse than the other
side", so add a second choice, without really looking into whether X really
is better or worse. Most systems would then make X win, even if they would
be crushed by either in an actual runoff where the voters actually took a
serious look at them.


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