Schulze, SEC, & many candidates

Mike Ositoff ntk at
Fri Oct 16 22:58:14 PDT 1998

> I have NEVER said that random-filling cannot back-fire.  That isn't
> my point at all.  My SEC criterion has nothing to do with a no 
> back-fire situation.  
> Consider a voter who prefers A > B > C.  We would hope that such a
> voter would vote sincerely.  However, his vote of B > C, could
> back-fire, and prevent A from being elected.  This is true of
> any Condorcet method.

Only if offensive order-reversal is used against A, and A
is a middle CW. That's the only time when A, a CW, can
lose because you ranked someone after him. Without offensive
order-reversal, no defensive strategy is needed, in VA, to
protect the win of a CW.

That isn't true with Margins.

> So, why would a rational voter vote sincerely?  Would the voter be
> forced to weigh their desire to get A elected versus their desire to 
> defeat C?  Actually, no.  Because even though the B > C ranking CAN
> defeat A, it could also elect A.  Unless the voter has knowledge
> of how everyone else is voting, the rational vote is A > B > C.
> Under VA, the rational voter uses the random-fill strategy.  Of

Maybe some would, but I've written at length about why it isn't
a problem with VA, even if it happens.

> course it can back-fire, but so can any rankings beside the first
> and the last.  Should I be paralyzed by fear of a possible back-fire
> into not voting a full ranking?
> An interesting problem with VA, which I have previously not methioned,
> is that it requires the kind of weighing of interests I mentioned above.
> For example, if I sincerely rank A > B > C, I could vote this way.
> However, I can increase the likelihood C will be defeated by voting
> A = B > C.  In other words, to have the most effective vote against
> C, I must not express my preference between A and B.  Of course, this 
> sort of weighing of interests is one of the most obvious characterstics
> of Approval, but it seems out of place in a ranked method.

It's very much out of place in a ranked method. It's never needed
in VA, for protecting a CW, except if offensive strategy uses
an impossible degree of predictive knowledge and sophistication.
Offensive strategizers would have to not only create a cycle with
their order-reversal. They'd have to also engineer a subcycle
in which everyone is majority-beaten. Forget it.

You're right, having to rank a less-liked alternative equal to
your favorite is something that has no place in a ranked method.
That's why Margins isn't worthy of rank-balloting. I've posted
several examples where, in simple ordinary typical situations,
with mere truncation causing the cycle--maybe innocent
non-strategically-intended truncation, you're forced to vote
the CW equal to your favorite in order to protect his win.
Unless the CW's voters know which side will truncate and
maybe rank a less-liked alternative over a more-liked one.

So thanks for bringing that out.


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