[EM] (3) MJ -- The easiest method to 'tolerate'

[Jameson Quinn]

Once again, I'm going to stand behind my view that U/P is a better
practical reform proposal than IBIFA, and that there are cases where U/P
gets the right answer and IBIFA doesn't. But once again, I'm going to
preface it by saying I think IBIFA is a great method overall.

So. Remaining debates.

Condorcet versus Majority Condorcet: I do not believe in the concept of
"irrelevant ballots", or that we should "simplify" a scenario by removing a
balanced set of ballots.

Dominant in top-ratings: taking this as a strong argument for who the
correct winner is, is inherently subject to clone effects. My "unserious"
example was a (serious) attempt to show this.

"It seems that you want a quite complicated method with a nearly as strong
as possible truncation incentive and that nearly always
simply elects the Approval winner (while somehow "tending to respect"
majority Condorcet without actually meeting the Majority
Condorcet criterion)."

I am completely baffled by the idea that IBIFA is less complicated than
U/P. If you want to, we can each post a 3-minute video where we explain our
method to a random "person on the street" and then ask the person to
explain it back to us. I'll bet that this would show U/P as far simpler to
understand. If you agree, I'll let you set any reasonable procedure for
each choosing our subject/explainee.

I also don't agree that the U/P has a "nearly as strong as possible
truncation incentive" or "nearly always simply elects the approval winner".
On the first point: I think that in a chicken dilemma situation, U/P would
lead to less truncation than many other methods, including things like MCA
or MJ, because in U/P, chicken truncation is only helpful precisely insofar
as it's risky. On the second: I think that there is a not-insignificant
subset of voters who strongly want to cast a ballot that's expressive
enough to distinguish their favorite from their preferred frontrunner. In
approval, such people would bullet vote; in U/P, they could still rate the
compromise frontrunner as acceptable. This could easily lead to different
(and better) outcomes.

2016-09-07 15:01 GMT-04:00 C.Benham <cbenham at adam.com.au>:

> On 9/7/2016 10:15 PM, Jameson Quinn wrote:
>
> C: C is the clearly voted Condorcet winner
>
> But not the majority Condorcet winner. I regard majority Condorcet as
> something any good voting system should tend to respect, but non-majority
> Condorcet as only a weak signal.
>
>
>
> C: The Majority Condorcet winner is always the Condorcet winner.  It is
> ridiculous to suggest that failing to elect a Condorcet winner is a step in
> the
> direction of  "tending to respect the majority Condorcet winner".
>
> The "Majority Condorcet" concept is vulnerable to Irrelevant Ballots, and
> to put it forward as some especially desirable criterion is nonsensical.
>
> In our example, would removing 3 plumping ballots from each of the
> candidates really turn C into a stronger candidate?  Because the effect
> would
> be to change C from a mere Condorcet winner (who you say should lose to
> the approval winner) into a fabulous  Majority Condorcet winner (who you
> say the method should "tend" to respect).
>
> (The only point of the criterion is that some methods happen to be able to
> meet it, but not the normal Condorcet criterion.)
>
> 20: A>B
> 25: B>A
> 20: C>B
> 26: C
>
> 91 ballots.  Majority threshold = 46.
>
> C > B  46-45,    C > A 46-45.
>
> Or of course the question can be posed the other way: does giving each
> candidate 3 extra plumping ballots really make C a weaker candidate?
>
> Whoops... I'm sorry. Those were the averages over a large number of polls,
> but then a week before the election, A had a heart attack. The actual
> scores, with 3 ballots still to count from A's former stronghold precinct,
> are:
>
> 48: B
> 49: C
>
> I guess C wasn't so dominant in top-ratings after all. Once we count those
> last three ballots, we'll have a clear winner here, and there's every
> chance it could be B.
>
>
>
> C:I take it this is Jameson not being serious (and perhaps trying to shift
> goal-posts).
>
> One of  IBIFA's obvious advantages over  "U/P" and MJ and the other
> Bucklin methods is that it has a
> much weaker truncation incentive.  In the example (with 100 ballots)  U/P
> penalised the 20 C>B voters
> for not truncating. Had they done so C would have won. (Unsurprising,
> since that would have made C positionally
> dominant as well the Condorcet winner).
>
> It seems that you want a quite complicated method with a nearly as strong
> as possible truncation incentive and that nearly always
> simply elects the Approval winner (while somehow "tending to respect"
> majority Condorcet without actually meeting the Majority
> Condorcet criterion).
>
> BTW, I'd be mildly interested in seeing one or two of your realistic
> examples where U/P doesn't elect the Approval winner.
>
> Given from what I can make of your method goals, why don't you simply
> propose  Majority Condorcet//Approval ?
>
> Chris Benham
>
>
>
> 2016-09-07 8:17 GMT-04:00 C.Benham <cbenham at adam.com.au>:
>
>>
>> 3: A
>> 20: A>B
>> 25: B>A
>> 3: B
>> 20: C>B
>> 29: C
>>
>> C > B  49-48,   C > A 49-48,   B > A 48-23.
>>
>> Top Ratings scores:   C 49,   B 28,   A 23
>>
>> Approval scores:      B 68,   C 49,   A 48.
>>
>> On 9/7/2016 7:09 AM, Jameson Quinn wrote:
>>
>> IBIFA elects C. U/P elects B. It's clear to me that B is better. The 3
>> A-only voters are likely attempting a chicken strategy.
>>
>>
>> C: C is the clearly voted Condorcet winner
>>
>
> But not the majority Condorcet winner. I regard majority Condorcet as
> something any good voting system should tend to respect, but non-majority
> Condorcet as only a weak signal.
>
>
>> and by far the most top-rated candidate.
>>
>
> Whoops... I'm sorry. Those were the averages over a large number of polls,
> but then a week before the election, A had a heart attack. The actual
> scores, with 3 ballots still to count from A's former stronghold precinct,
> are:
>
> 48: B
> 49: C
>
> I guess C wasn't so dominant in top-ratings after all. Once we count those
> last three ballots, we'll have a clear winner here, and there's every
> chance it could be B.
>
>
>> The suggestion that "B is better" because of
>> some guess that 3 truncators are "likely" attempting some strategy is
>> absurd.
>>
>
> No, B is better because B has majority approval where C is rejected by a
> majority. The argument about likely truncation is merely how IBIFA went
> wrong, not how U/P got it right.
>
> ...Again, I don't regard this as a knockdown argument against IBIFA. It's
> only one scenario; a roughly plausible one, but not particularly likely. I
> think we should probably drop this. But I do think it demonstrates pretty
> conclusively that IBIFA at least isn't strictly dominant. After all, as
> long as we're making up arbitrary scenarios, we can arbitrarily assume that
> the 3 A voters are in fact attempting strategy. Punishing strategy might
> not be the worst thing in the world, but rather than punishing 48 voters
> for the strategy of 3, it would be better to ignore the 3.
>
> I'll write a broader response in a minute.
>
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>
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