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<span class=""><span>43: A<br>
24: B>C<br>
23: C>B<br>
10: D<br>
<br>
</span></span><br>
<span class=""><span>On 9/11/2016 4:21 PM, Jameson Quinn wrote:<br>
<br>
</span></span>
<blockquote type="cite">I think that scenarios like the above are
fundamentally pathological; any possible winner has only
minority approval, so that even assuming all ballots are
semi-honest, any of them could be a true Condorcet loser.</blockquote>
<br>
C: I can't see anything "pathological" about the "scenario". The
ballot set can be taken at face value. Presumably the A and D
supporters simply aren't interested in any candidate<br>
other than their favourites, while the B and C supporters form a
tight coalition. And B is the clearly voted Condorcet winner.<br>
<br>
Just because you can imagine that with less truncation some other
candidate could have been the Condorcet winner doesn't mean that
the scenario is in any way "pathological".<br>
<br>
<blockquote type="cite"> J: Thus, I believe that it's more
important for a system to try to avoid scenarios like the above,
than to try to find a perfect winner in such a scenario.</blockquote>
<br>
But there isn't (or shouldn't be) anything difficult about
finding "the perfect winner" in the scenario. B is the plainly
voted Condorcet winner. An Approval-like method<br>
might mistakenly elect the "similar" candidate C, but A and D are
out.<br>
<br>
And if I agreed that a system "should try to avoid" such a
scenario, I can't see how it could (allowing 4 candidates and
using ballots with 3 or more ratings slots).<br>
<br>
<blockquote type="cite">43: A<br>
40: B>C
<div>6: C>B<br>
1: C<br>
10: D<br>
</div>
<div><br>
</div>
<div>J:... I think that a case can be made for either A or B.
After all, they'd be tied if we try to approximate Score by
using truncatable Borda here. But no serious case can be made
for C or D, even though C wins MTA and MCA.</div>
</blockquote>
<br>
The pairwise-dominant B,C coalition is still intact. Without the
irrelevant D ballots it has more than half the votes. B is still
the CW, C is the most approved ("accepted", voted above bottom)<br>
candidate. B is also more approved than A. That adds up to no case
for A.<br>
<br>
<blockquote type="cite"> J: After all, they'd be tied if we try to
approximate Score by using truncatable Borda here</blockquote>
<br>
C: In my opinion that is a bizarre and very weak standard. Those
methods don't even meet Majority Favourite, and Borda has other
problems.<br>
<br>
<blockquote type="cite"> J: But no serious case can be made for C
or D, even though C wins MTA and MCA.</blockquote>
<br>
C: C is the most approved candidate and pairwise beats all the
others except B, and all of B's supporters approved of C (which
arguably somewhat weakens any post-election complaint<br>
they might make, since MTA and MCA are quasi-Approval methods
that aren't advertised as meeting the Condorcet criterion.)<br>
<br>
Another 3-slot FBC method I think we should be comparing with
these three is 3-slot TTR,TR (aka" ICT"). The algorithm is
probably too complicated to interest Jameson<br>
as a practical reform proposal, but it meets Chicken Dilemma and
"Majority Condorcet" and easily elects the CW in the recent
examples.<br>
<br>
<blockquote type="cite">J: One possible alternative default rule:
ballots alternate between defaulting to "acceptable" and to
"unacceptable". Each ballot clearly states which default it
uses, and there is a place on the ballot to globally change that
default. (I doubt Chris will like this idea, but it is at least
straightforward, explicit, and easy to describe.)</blockquote>
<br>
I'm strongly of the view that the voters shouldn't have to bother
explicitly marking candidates they rate as unacceptable. I suggest
a ballot instruction something like:<br>
<br>
"Among candidates you find acceptable, mark however many you like
of your favourites as Preferred and the rest as Acceptable".<br>
<br>
However, if there was a concern that someone might get access to
the ballots after they're cast and before they are counted and
alter some by adding marks to<br>
candidates the voters left unmarked, then that could be
justification (or a pretext) for a draconian Australian-style
solution with a ballot instruction like:<br>
<br>
"Mark each candidate as one of Preferred, Acceptable,
Unacceptable. You must mark every candidate."<br>
<br>
Then ballots that don't mark every candidate are declared
"invalid" and have no effect on the election result. <br>
<br>
One more semi-sane alternative is to have a ballot instruction
like the Australian-style one but make the default "acceptable"
under MTA and MCA and "unacceptable"<br>
under U/P but in each case with a weight of one half in the
counting. (But of course that doesn't completely remove the
incentive for some cheater to add marks to<br>
ballots).<br>
<br>
Chris Benham<br>
<br>
<br>
<span class=""></span><br>
<br>
On 9/11/2016 4:21 PM, Jameson Quinn wrote:<br>
</div>
<blockquote
cite="mid:CAO82iZysLUc3mOTKo1kcJAfxPzbAm4aRWB5=EiS=pTmbEAq=Gw@mail.gmail.com"
type="cite">
<div dir="ltr">
<div class="gmail_quote">
<div dir="ltr">
<div class="gmail_extra">
<div class="gmail_quote"><span class="">2016-09-10 21:26
GMT-04:00 C.Benham <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:cbenham@adam.com.au" target="_blank">cbenham@adam.com.au</a>></span>:<br>
<blockquote class="gmail_quote" style="margin:0px 0px
0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex"><span>On
9/11/2016 5:02 AM, Kevin Venzke wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0px
0px 0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
43: A<br>
24: B>C<br>
23: C>B<br>
10: D<br>
<br>
Under MTA the B and C voters are being
completely reasonable: They hope for majority
approval but can still hope for a win if they<br>
don't get it.<br>
<br>
Strategy is less likely to produce these ballots
under U/P because the B and C voters are taking
a gamble. To get a similar outcome<br>
they have to vote B=C. Anyone who doesn't is
functionally defecting!<br>
</blockquote>
<br>
</span>
C: A very good example! Assuming MTA and MCA use
Top Ratings scores to break Approval ties, they both
elect the Condorcet winner B.<br>
</blockquote>
<div><br>
</div>
</span>
<div>J: But both could be shifted to C with a single
C-only ballot, even if the B:C ratio were 46:1 instead
of 24:23.</div>
<span class="">
<div> </div>
<blockquote class="gmail_quote" style="margin:0px 0px
0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<br>
C: U/P's under-use of the middle ratings slot means
that it relies more on its "majority
disqualification" mechanism which seems to make it
more<br>
vulnerable to irrelevant ballots, as in the example.<br>
<br>
Under U/P, without the irrelevant D ballots, A and D
are disqualified and B is the glorious winner. With
them, B and C and D are disqualified and (without
needing<br>
any others to be disqualified) A wins.<br>
<br>
This causes me to reject U/P as clearly worse than
MTA and MCA. Of the three I (again) rate MTA as the
least bad.<br>
</blockquote>
<div><br>
</div>
</span>
<div>J: I think MTA is pretty darn good. I still prefer
U/P.</div>
<div><br>
</div>
<div>I think that scenarios like the above are
fundamentally pathological; any possible winner has
only minority approval, so that even assuming all
ballots are semi-honest, any of them could be a true
Condorcet loser. Thus, I believe that it's more
important for a system to try to avoid scenarios like
the above, than to try to find a perfect winner in
such a scenario. In fact, in the related scenario:</div>
<div><br>
</div>
<div><br>
43: A<br>
40: B>C</div>
<div>6: C>B<br>
1: C<br>
10: D<br>
</div>
<div><br>
</div>
<div>... I think that a case can be made for either A or
B. After all, they'd be tied if we try to approximate
Score by using truncatable Borda here. But no serious
case can be made for C or D, even though C wins MTA
and MCA.</div>
<div><br>
</div>
<div>Anyway, I think U/P does a better job trying to
discourage the kind of strategy that would lead to a
scenario like the above. And part of that is the
default rule which Chris has criticized.</div>
<div><br>
</div>
<div>One possible alternative default rule: ballots
alternate between defaulting to "acceptable" and to
"unacceptable". Each ballot clearly states which
default it uses, and there is a place on the ballot to
globally change that default. (I doubt Chris will like
this idea, but it is at least straightforward,
explicit, and easy to describe.)</div>
<div><br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px
0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
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