[EM] question/comments re DMC

[Jobst Heitzig]

Dear Warren!

You wrote:

>>1. Allows to distinguish important from minor preferences. 
> --range does too, only better.

OK.

>>2. Immunity from second place complaints. Unlike in MinMax and 
>>Beatpath, the DMC winner always defeats the candidate which would win
>> if the winner were not present. 
> --nice. Also true of range.

I'm sorry you're wrong here: If ballots are

  voters  A points  B points
    60       60        40
    40        0       100

then B wins although she is obviously defeated by A, the obvious 2nd
place winner.

>>15. [related to 3] Defeats other methods. In every situation, the DMC 
>>winner is either identical to or defeats the winner of each of the 
>>following methods: Approval Voting, Condorcet//Approval, 
>>Smith//Approval, DFC, TAWS.
> --I consider this criterion 15 to be artificial.  No matter what ranked ballot method you
> have (X) I con construct a new one Y so the Ywinner always is same as or beats the Xwinner
> pairwise.  In particular I can make X=DMC to get Y=a method that pairwise beats DMC...
> This fact suggests to me that this criterion is meaningless...

I would say that when explicitly comparing two seriously suggested
methods, it is well significant if the winner of the first always
defeats the winner of the second.

>>6. Robustness against "noise" candidates.. cloneproof...
> --also true of range.

Could you say more precisely what you mean here?

>>7. Easy and transparent algorithm. 
> --way truer of range...

I agree.

>>8. Robustness against counting errors. Since DMC uses only the 
>>ordering by approval score and not the precise approval scores, and 
>>uses only the direction of the pairwise defeats...
> --sounds kind of silly claim to me, and anyhow is truer of range since range has
> fewer tie-possibilities that can matter.

Thanks for taking me serious and calling me silly :-)

>>9. Avoids margins/winning votes debate.
> --truer of range...

True, yes, but what do you mean by "truer"?

>>10. Avoids a discussion of "cycles"...
> --also true of range...  and probably truer...

see above.

>   M1:  interchange order of two neighboring candidates in your rank-order vote ==>
>      (A>B becomes B>A) cannot decrease B's chance of winning, cannot increase A's.
>   M2:  minimally change your vote so now approve of A ==> cannot decrease A's chance of winning.
> Which of these are true? Both?

Yes, both. Check out for yourself, it's quite easy.

>>17.  It is resistant to the burying strategy that plagues some
>>Condorcet methods.  This is related to reason number 9.
> --could you be more precise?

That was Forest's claim, I haven't thought about this so far.

Yours, Jobst