[EM] Every MMC example can just as easily be an IRV WDSC & FBC failurle example

[MIKE OSSIPOFF]

I'd said:

>As I was saying before, I often call MMC the "Fortuitous Special Case 
>Criterion), because it only applies in what, for a certain set of voters,
>is a fortuitous special case. But that case isn't so fortuitous for other 
>voters, and every example of that type leads to an IRV failure example
>for WDSC & FBC.

Please note that, there, I said "leads to", rather than "is". That will make 
a difference in regards to James' objection to that statement.

There's nothing at all implausible about supposing that the nonmembers of 
the mutual majorilty prefer the mutual majority candidate who needs their 
help to win in IRV to the other mutual majority candidate(s), or believe 
that that may be so, for all they know.  So it's true that every MMC example 
leads plausibly to an example in which IRV fails WDSC & FBC.

I'd also said:

>every MMC example is an IRV failure example in wihch IRV fails FBC & WDSC

I reply:

There I said "is". "Leads to" is better. But "could just as easily be" is 
better yet.
Replace "is" with "could just as easily be".

If it's unknown which mutual majority candidate will win in IRV, without the 
help of the voters not in the mutual majorilty, then, knowing that they 
can't possibly elect their favorite, they have incentive to help their 
favorite mutuial majority candidate. They gain nothing by not burying their 
favorite. They improve their expectation by burying their favorite. The 
example could pefectly well be an IRV WDSC & FBC failure example, from what 
those voters know. And if we're writing the example so that it's known which 
mutual majority candidate will win, then it's obvious that it could just as 
easily be written with defensive favorite-burial incentive in IRV.

And if James contrives the example so that the mutual majority candidate 
preferred by voters not in the murual majority wins under sincere voting, 
that could just as easily have been the other way. No implausibility. 
Writing it so that there's no IRV defensive reversal incentive is a 
misleading contrivance, since it could just as easily be the other way.

I withdraw "is", and replace it with "could just as easily be".

James also speaks of an example in which the "mutual" majority involves only 
one candidate.

In that case, with public knowledge of that "mutual" majority, IRV doesn't 
violate MMC or FBC. And Approval doesn't have a problem either. Voters don't 
have a dilemma, because they know they can't do anything about that 
candidate's majority.


James continued:


	First, let's say that you can consider a straightforward one-candidate
majority to be a special type of mutual majority. Then you can have
example where approval fails MMC and regular MC, but where there is no way
that any of the voters can benefit from order reversal in IRV.
	Here is such an example. These are the sincere preferences, and the >>
marks represent the approval cutoffs (rather than marking a stronger
preference, which is what I usually use them for).

42: A>B>>C
10: A>>B>C
2: B>>A>C
2: B>>C>A
44: C>B>>A

approval score
A: 52
B: 58
C: 42

	So, A is a straight majority winner, the first choice of a clear
majority. A would win with IRV, of course, if people voted sincerely.
Also, the voters who prefer B or C can reverse the order of their
preferences all they want but they still won't be able to change the
outcome. So there is no FBC or WDSC failure in this particular example.
	Of course, what approval fans will say is, "why would 10 of the ABC
voters be so dumb as to approve B?" Well, I can give you a plausible
scenario at least. Let's say that no one knew that A would actually have a
majority. Let's say that the A voters were worried about C winning, and
some of them saw B as the compromise candidate, and went ahead and
approved B. Sure, it's a bad calculation on their part, but it's not
unthinkable that they could make it. And it's really quite a damaging
example for approval, in my opinion, because the candidate who is the
first choice of a majority isn't elected.

I reply:

When I've made my claim about mutual majority examples, I've always said 
that it's known that the mutual majority exists for a certain set of 
candidates. Knowing that gives other voters incentive to bury their 
favorite. But if it's known that the "mutual" majority for A exists, then 
the A voters have no reason to vote for B.

Sure, given a lack of information about the majority, in Approval, some A 
voters might feel a need to vote for B. And, likewise, with such incomplete 
information, in IRV, some A voters might think that A doesn't have a 
majority, and that B is the  best that they can get, and that they need to 
help B by voting B in 1st place instead of A, because obvioulsy B doesn't 
have much favoriteness, and needs all the help s/he can get. So the mere 
belief that A doesn't have a majority will send A voters ranking B in 1st 
place.

It would seem that James wants to apply different standards to Approval and 
to IRV.

The difference? In IRV, those mistakenly compromising voters are burying 
their favorite by voting someone over hir. But not in Approval. That's why 
Approval, compared to IRV, requires twice as many mistaken compromisers to 
give away an election.

James continued:

	But this isn't the main point of this e-mail. I'm trying to keep it
simple, so what I'm saying is that not all examples where approval fails
mutual majority give incentive for order reversal in IRV.

I reply:

They all plausibly lead to such examples. They could all just as easily be 
such examples. And if the voters don't know who wins under sincere voting, 
but only know about the mutal majority, then in IRV they have incentive to 
bury their favorite.

So yes, I withdraw "is" in that statement, and replace it with  "could just 
as easily be".

James continued:

Okay, okay, you're not satisfied that a straight majority qualifies as a
mutual majority? Fine, it doesn't even have to be a straight majority, as
long as the dominant majority candidate (dominant from an IRV point of
view) is preferred to the other majority candidate(s) by voters outside
the majority. For example:

sincere preferences, plus approval cutoffs
10: X>A>B>>C
32: A>X>B>>C
10: A>X>>B>C
2: B>>A>X>C
2: B>>C>A>X
44: C>B>>A>X

[...]

Assuming an IRV tally, can anyone show me how any of the voters here can
reverse a preference or otherwise vote insincerely in order to get a
result that they prefer?
	I really don't see a way. I'm sure that someone will point it out if
there is one.
	But unless there is a way, I think that Mike's statement is inaccurate.

I reply:

The statement with "is" is inaccurate. The statement with "leads to" is 
accurate. And James is specifying information that could have just as easily 
been opposite. The nonmembers of the mutual majority could just have easily 
preferred the mutual majorilty candidate who needs their 1st ranking to win. 
  So, though "is" isn't accurate, "could just as easily be" is accurate.

I prefer "could just as easily be" to "leads to".

I withdraw "is" and replace it with "could just as easily be". That 
completely plausible IRV WDSC & FBC failure example is always  sitting right 
under the nose of the IRVers when they give us a mutual majority example, 
even if they've contrived to write it differently.

And if it seems as if I'm moving the goalposts, my point all along was just 
that the IRVers' mutual majority and clone examples bring out how easily IRV 
fails WDSC & FBC, two failures that IRVers like to claim are rare. Not rare. 
Every mutual majority example that IRVers show to us could easily and 
plausiblly be an example of IRV failing WDSC or FBC. And if the voters don't 
know, they have incentive to bury their favorite.

That' s what makes failure of FBC, WDSC & other defensive strategy criteria 
so bad: When information isn't complete and reliable, and it usually won't 
be complete and relilable, easy failures of those criteria can and will 
cause voters to give away the election if they believe that the such a 
defensive strategy criterion-failure situation exists in that election.

Maybe that's what they'll be doing this year, in fact.

Mike Ossipoff

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