[EM] Re: Rob: MDDA vs BeatpathWinner

[MIKE OSSIPOFF]

Rob--

You wrote:

The one major objection I have [to MDDA] is the lack of
truncation resistance - I really hope we can find a system that
encourages a full ranking.  It seems that MDDA would tend to discourage
ranking anyone below a plausible frontrunner, if I understand it
correctly.

I reply:

Not necessarily. For the person who needs and wants to make use of FBC 
compliance, then yes, that person will equal-top-rank the acceptables, and 
power truncate the unacceptables. If power truncation isn't available, then 
s/he will truncate them or rank them in reverse order of winnability.

Likewise, s/he'd sometimes rank the unacceptables in reverse order of 
winnability in BeatpathWinner, if offensive-order-reversal deterrence isn't 
the primary consideration. S/he must judge if offensive order-reversal is a 
threat, and, based on that, whether to truncate or strategically rank. With 
MDDA there similarly would be a choice between truncation and strategic 
ranking. Truncate if you think you can best beat all the unacceptables in 
the Approval count. Strategically rank if you think you can best beat them 
all by making majority defeats against eachother. With power truncation you 
don't have that concern: Just power truncate them. Much simpler than 
BeatpathWinner or unenhanced MDDA).

But I'm saying that SFC compliance is for the person who doesn't need FBC, 
for the sincere voter. If you believe you're in a sincere-voting majority, 
then you can freely rank all the candidates, and you're assured that no one 
that your majority like less than the CW will win. That doesn't require any 
truncation, or any kind of strategy.

So it isn't that MDDA forces you to truncate. It depends on which 
criterion-compliance you want to use, which kind of strategy you want to 
use, what kind of a voter you are. The two kinds of strategy, the mix of 
criterion-compliances, makes MDDA more versatile than BeatpathWinner.

You continued:

I'd also really like to rename SFC to something that is more descriptive
of what's measured.  If a system encourages truncation, it can't
truthfully be called "strategy free".

I reply:

I haven't named MDDA "Strategy-Free". When Kevin devised and introduced 
MDDA, we agreed on the name MDDA.

But MDDA is indeed strategy-free for a majority with the conditions and goal 
described in SFC. SFC describes condidtions under which a majority can 
ensure that no one worse than the CW wins, without using any strategy, with 
complying methods. So yes, SFC is about strategy-freeness, where it's 
possible.


Such subjective titles don't
serve us well anyway.  "Majority Pairwise Winner" would be an accurate
and suitable name, but certainly not the only one.

I reply:

The words strategy-free describe SFC's guarantee. Strategy-freeness where 
it's possible.

You continued:

I've contemplated
"Majority Condorcet Winner", but using "Condorcet" in the name isn't
helpful, since I don't think Condorcet ever proposed anything like that.

I reply:

That Condorcet didn't propose SFC, or a name for it, doesn't mean that it 
wouldn't be appropriate to name SFC for its protection of CWs, or its 
relation to the Condorcet Criterion.

I sometimes refer to SFC as Condorcet's Criterion for majorities. And I 
sometimes refer to GSFC as the Smith Criterion for majorities.

I have no objection to those names in the paragraph before this one.  If 
others prefer them, I'd be glad to use them. Then, I'd capitalize 
"Majorities", so the criteria would be "Condorcet's Criterion for 
Majorities" and "The Smith Criterion for Majorities".

But I feel that "Strategy-Free Criterion" describes what makes them the 
pinnacle of the promise of rank-balloting.

Mike Ossipoff

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