# [EM] FBC comparison: WV, margins, MMPO, DMC

Wed Sep 7 15:36:53 PDT 2005

```On 9/7/05, Kevin Venzke <stepjak at yahoo.fr> wrote:

> The methods are quite different in the case where it is sufficient to
> *weaken* the strength of the A>B win without needing to reverse it.
>
> In WV and MMPO (that is, MinMax(pairwise opposition)), there is never
> favorite betrayal in this case, because changing the vote A>B to A=B is
> no more effective than changing it to B>A. Every voter making this change
> reduces the A>B strength by 1 vote.
>
> But in margins, favorite betrayal always works twice as fast as equal
> ranking. Changing A>B to A=B shrinks the margin by 1 vote, while changing
> it to B>A shrinks the margin by 2 votes. Sometimes B>A is going to be the
> only way to weaken the defeat sufficiently.
>
> In DMC, neither A=B nor B>A is effective. The only ability you have to
> weaken
> the A>B win (assuming you can't reverse it) is to disapprove A!

This seems to imply the possibility of favorite betrayal in a pretty common
case. Say your sincere ranking was A>B>cutoff>C. Furthermore, assume that
your approval of B is important to maintaining the strength of the B>C
defeat. If it was necessary to reduce the strength of the A>B win, wouldn't
the necessary strategic vote then become B>cutoff>A>C, i.e. favorite
betrayal?

(My FBC simulation doesn't envision favorite betrayal of that kind, so I
> would have to rethink it in order to find statistics for DMC relative to
> WV and margins.)

I think that would be worth looking into. My guess (and I stress that it is
only a guess) is that DMC would have favorite betrayal incentive less often
than margins, but significantly more than wv.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.electorama.com/pipermail/election-methods-electorama.com/attachments/20050907/348439fa/attachment-0003.htm>
```