[EM] "Guaranteed Majority criterion" on Electowiki

[Kevin Venzke]

Hi Chris,

--- En date de : Mer 3.11.10, C.Benham <cbenhamau at yahoo.com.au> a écrit :
>>The guaranteed majority criterion requires that the winning candidate 
>>always get an absolute majority of valid votes in the last round of 
>>voting or counting. It is satisfied by runoff voting, MCA-AR, and, if 
>>full rankings are required, IRV. However, if there is not a pairwise 
>>champion (aka CW), there could always be some candidate who would have 
>>gotten a majority over the winner in a one-on-one race. Since, unlike 
>>most criteria, this criterion can depend on both counting process and 
>>result, there could be two systems with identical results, with only one 
>>of them passing the guaranteed majority criterion. 
>
>This is an example of what Mike Ossipoff used to rightfully excoriate as 
>a "rules criterion".
>
>To me if  "two" voting systems/methods always give the same results with 
>the same impute, then they are really 
>just one method (which perhaps has alternative algorithms) and so they 
>both meet and fail all the same (non-silly)
>criteria.

Yes, I imagine criteria to be defined based on the results of the method,
not the procedure for finding the result...

A good reason for this is that there is no objective test for what
constitutes a "round of counting" or "getting" a vote in such a round. Or
even what is a "valid" vote: It's not obvious that two-vote runoffs should
satisfy the criterion. I guess in a "round of voting" the "valid votes"
are determined based on the current (i.e. last) round but in a "round of
counting" you use all the votes cast and not just those still being
evaluated.

I can't help but notice that MCA-R or -AR are not even methods, but 
classes of methods... MCA-AR methods satisfy the criterion purely because
they end in a two-round runoff. Why not generalize the article to say
that instead??

Kevin