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

Jameson Quinn jameson.quinn at gmail.com
Wed Sep 7 05:45:38 PDT 2016

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,

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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