[EM] Cardinal Pairwise: Guilty till proven innocent

[MIKE OSSIPOFF]

James said:

They [voting systems] must be
assumed to be assumed to be worse than the status quo until it can be very
conclusively demonstrated that they are better.

I reply:

Plurality violates the Condorcet Loser Criterion, when that criterion is 
written in preference form so that it applies to all methods. WV, other than 
PC,  passes Condorcet Loser.

In Plurality, even if everyone prefers X to Y, they might believe that Y is 
the lesser-evil whom they need in order to keep Z, whom they dislike more, 
from winning, and therefore give their votes to Y. Plurality can elect Y 
when everyone prefers X to Y.

So those can't be the ways that WV can fail in a ways thats Plurality won't 
fail.

But wait....Does Cardinal Pairwise pass Participation and Consistency? Did 
you know that Plurality passes those criteria?

James, you can't expect us to take Cardinal Pairwise seriously till you show 
that it's potentially serious violations of Participation and Consistency 
aren't going to be serious problems. How you're going to prove that, I have 
no idea. But you must prove it before Cardinal Pairwise can even be 
considered.

What's that? You think it means something that Cardinal Pairwise passes 
criteria that Plurality doeesn't pass? But how are you going to prove that 
those criteria are as important as Participation and Consistency? How are 
you going to prove that, in some unforseen way, Cardinal Pairwise's failure 
of Participation and Consistency won't cause a worse problem than the 
problems that Plurality causes when it violates the criteria that Cardinal 
Pairwise meets? Remember, you have to prove that.

Until you can prove that, there is a method that is _already_ known to be 
better than Pluralitly in every way: Cardinal Ratings. Of course Approval is 
one version of CR. CR passes Participation and Consistency, and additionally 
passes FBC and WDSC, two criteria that Plurality fails.

I don't know if you can find a criterion that Plurality passes and CR fails. 
How silly a criterion will you have to come up with, in order to find one 
that Plurality passes and CR fails?

CR differs from Plurality only in giving more freedoms to the voter. 
Plurality is a point system with the peculiar rule that the voter may give a 
1 rating to only one candidate, and is required to give a 0 rating to all 
the others. In contradistinction, CR lets the voter give any point rating, 
within the method's points-range, to any candidate.

That's true in Approval too, of course. But the other CR versions of course 
give voters additional freedom when they allow a wider range of points 
assignments to candidates.

Unless you can prove that Cardinal Pairwise's failure of Participation and 
Consistency won't cause a serious problem, then you can forget about CP.

You continued:

Or, they should be assumed
to have every conceivable problem until it can be conclusively
demonstrated that they don't have that problem. Why? Because the integrity
of the voting system is a very serious thing to risk.

I reply:

Then let's not risk making things worse by replacing Plurality with a 
Consistency and Participation-failing rank method. Borda meets 
Participation. Does it meet Consistency?

But Borda fails Majority Favorite, a simple votes-only criterion reasonably 
met by Plurality and CR.

Mike Ossipoff

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