[EM] Allow equal ranking

[MIKE OSSIPOFF]

You wrote:

>Or is equal-ranking important for other strategic reasons, to avoid 
>requiring Favorite Betrayal?

In the wv methods, including MAM, equal-ranking is one of two 
anti-order-reversal strategies.

These two strategies are defensive equal ranking and defensive truncation.

In the example where the A voters order-reverse to steal the election from 
B, the CW:

Defensive truncation would mean the B voters not voting for A. In general 
the strategy would be to not vote a 2nd choice at all.

Defensive equal-ranking would mean the C voters moving B up to share 1st 
place with C.

The advantage of equal ranking is that it isn't a dominated strategy. It 
elects the CW. The C voters gain from it.

Defensive truncation is a dominated deterrent strategy. If the A voters 
order-reverse and the B voters truncate, then C will win. If the B voters 
prefer A to C, then the argument is that they've made things worse for 
themselves.

But defensive truncation, unlike defensive equal-ranking, _deters_ offensive 
order-reversal.

If you use a strategy that doesn't deter offensive order-reversal (and we're 
assuming an electorate where anti-order-reversal strategy is needed), then 
you'd better be prepared to use it all the time, because there's no penalty 
for offensive order-reversal that is thwarted, no reason for them to not 
give the offensive order-reversal a try. Nothing for them to lose from it.

Not only will you need that defensive equal ranking all the time, for the 
un-deterred offensive order-reversal, but that strategy asks a lot of you, 
ranking 2nd choice equal to 1st choice.

For the people who believe that their favorite is CW to not vote a 2nd 
choice is a mild requirement.

And B is their candidate, so aren't they the ones who should protect hir?

And dominated deterrent strategies work. As I said, they're in wide use in 
the animal kingdom and in legal systems. If truncation, whether strategic, 
principled, whimsical, or emotional, is widespread, then people will be 
deterrred from offensive order-reversal.

To return to the question, equal ranking should be allowed, partly because 
people might consider 2 candidates equal. Partly because it's one of the 2 
anti-order-reversal strategies. And also because if, like me, you consider 
the candidates classifiable into 2 sets such that the merit differences 
within each set are negligible compared to the merit differences between the 
2 sets, then it's to your advantage to rank all the better-set candidates 
together in 1st place. So I wouldn't want to give up equal ranking.

It may well be that NES(Approval), or NES(wv), or NES(NES(wv)) can get rid 
of the incentive for me to equal rank all the better-set candidiates 
together in 1st place. But until that has been accomplished, I prefer to 
keep the option of equal-rankig.

Mike Ossipoff

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