[EM] Part 2, Re: James, SFC

[MIKE OSSIPOFF]

James--

You say:

By the way, we should try to solidify this a bit. Do you think that
"always truncate after your approval cutoff when a burying strategy
(offensive strategy) is a possibility" is good universal advice for voters
in WV elections.

I reply:

For the purpose of that question, let's assume that anti-OOR strategy is the 
only reason to truncate, though I've stated a lot of other reasons to 
truncate.

In a devious electorate that would be one thing that could be recommended. 
Or just don't rank anyone but your favorite if you believet that your 
favorite is CW and that the electorate is devious. Or just don't rank anyone 
whose voters are likely to attempt OOR against your favorite.

I emphasize those suggestions are only for a devious electorate. I wouldn't 
suggest those anti-OOR strategies with our electorate unless it turns out 
that there is an OOR problem.

And, as I said, I'd ask people to not rank anyone who, like John Dean, 
doesn't deserve a vote, just as I ask people to not vote for them now, with 
Plurality, and would ask people not to vote for them in Approval, and would 
ask people to give them minimum points in CR.

I'd said:

But, under the plausible conditions under which such a
>guarantee can be made, wv makes it, because wv meets SFC.


You continued:

	Methods that use information other than rankings (like CWP, AERLO/ATLO)
can make it so that voters have more freedom to vote their full sincere
rankings while still employing effective counterstrategy.

I reply:

The fact that AERLO/ATLO further reduces strategy incentives or needs 
doesn't change the fact that SFC-complying methods offer the guarantee that 
I stated under the conditions when it can be offered.

CWP? Absolutely not, unless you patch it for that purpose, via that 
majoritiy patch that you spoke of.

I'd said:

>One other thing that you're forgetting: While offensive order-reversal is
>an extreme and drastic offensive strategy, truncation needn't even be an 
>offensive strategy at all.

	I agree with this; I'm not forgetting it. I also remind you above that
order-reversal is not always done with a specific strategy in mind.

I reply:

Good, then you understand that for a pairwise-count method to not have a 
problem when nonstrategic truncation takes place makes a very big 
difference. And the possibility that wv, like CWP, can still be affected by 
OOR doesn't mean anything as a way to try to say that SFC's guarantee isn't 
important.

That isn't what you're trying to say? Then I don't know what you're trying 
to say. Why don't you figure that out before you post again.

You continue:

[...]

I reason that CWP won't be
vulnerable to truncation in practice, despite the SFC failure. Recall that
the ratings are the determinant of defeat strength in CWP. If I truncate
when I get to candidates at the bottom of my utility range, it usually
won't make much difference, because even if I did rank them out, I would
rate them close to zero anyway. Either way, my ballot doesn't lend much
strength to defeats between them, and my ballot lends close to maximum
strength to defeats where they are beaten by a candidate whom I rate
highly. Hence, I think that only a remarkably low-utility CW could be
deprived of victory in CWP as a result of this kind of non-strategic
truncation.

I reply:

Often voters  in CWP would have to choose the strategically best ratings in 
order to secure the protection that SFC complying methods give 
automatically.

You continue:

	I also argue that CWP won't be vulnerable to strategically motivated
truncation. If supporters of a candidate A are truncating against B (the
sincere CW) in order to cause an A>C>B>A cycle that resolves in favor of
A, I reason that A and B are likely to be very different candidates, in
that the average rating differentials on both sides of the A-B preference
will be high. (If they were similar candidates, then the reward/risk ratio
of the strategy would be fairly low, and hence it would probably not
occur.) If the rating differential on both sides of the A-C preference is
high, then the B>A defeat will be strong, and an attempt to overrule it
via a burying strategy will be unlikely to succeed.

I reply:

That somewhat mitigates the problem, but doesn't change the fact that often 
voters in CWP will need to guess the best ratings strategly in order to gain 
the protection that is automatic with SFC complying methods.

You say:

I do say that order-reversal may be more likely than
you expect

I reply:

Remember the story of the Three Sillies and the hammer on the wall?

You continue:

, and that CWP can provide similarly high resistance to both
truncation and order-reversal.

I reply:

You mean similarly _low_ , when compared with SFC-complying methods' 
resistance to truncation.

You continue:

	I'm not arguing with you on the WV versus margins question. I believe
that WV is substantially better (as you say, more stable). I also think
that GSFC is a useful criterion. However, I do say that CWP's GSFC failure
will not have the practical significance that you might expect, and that
CWP (without the majority-beats patch) will still be more
strategy-resistant than WV. As I wrote earlier, CWP has anti-strategic
properties that make it highly resistant to both truncation and
order-reversal.

I reply:

Against truncation CWP's protection is haphazard compared to the assurance 
of SFC & GSFC. Against order-reversal, yes, if people know how to use their 
ratings strategically to gain what AERLO and ATLO could give.

You continue:

I suggest that these properties are too subtle to be
measured by existing ranked ballot criteria, because they work based on a
(hopefully correct) understanding of the interaction between strategy and
preference strength, and preference strength information is not included
in ordinal data.

I reply:

I said that, as far as I know, until I find out different, CWP gives the 
benefits that AERLO and ATLO add to wv, though CWP doesn't give the very 
real benefits that wv gets from SFC and GSFC compliance. Unless you add that 
majority patch.

You can't talk your way out of that.

Mike Ossipoff

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