[EM] MOP-F2 / Non-Drastic Defense

Juho Laatu juho.laatu at gmail.com
Mon Jul 8 11:01:40 PDT 2019

> On 08 Jul 2019, at 17:36, C.Benham <cbenham at adam.com.au> wrote:

>> Margins provide good results with sincere votes, so why not use margins...
> I don't see how egregious failures of the Plurality  and Later-no-Help (and even Non-Drastic Defense) criteria constitute "good results"
> irrespective of whether the votes are "sincere" or not.

I googled the Non-Drastic Defense criterion and this example.

46 A>C
10 B>A
10 B>C
34 C=B

Non-Drastic Defense criterion:    if on more than half the ballots X is voted both above Y and below no other candidate (i.e. no lower than equal-top) then Y must not win

The Non-Drastic Defense criterion says that A should not be elected.

If no cutoffs are used, MOP-F2 is the same as the base method, i.e. Minmax(margins), and elects A. But if those 34 voters that seem to consider C and B to be clones indicate this in their votes (as they probably should) by voting C=B>>, C>B>>, or B>C>>, then B wins.

I guess it would be ok in MOP-F2 not to support use of "=" in the vote (explicitly) since in this case since they can vote also C>B>>, or B>C>>, and by doing this, indicate that these two candidates should be seen as clones / their mutual defeats should be seen as weak defeats.

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