# [EM] Re: Approval STV

Forest Simmons fsimmons at pcc.edu
Mon Apr 5 14:43:02 PDT 2004

```Interesting idea.

In this context (where Approval scores are used to eliminate candidates)
it might be better to use reverse weighted mean approval (RWMA).

To me it seems that RWMA would be best if relatively few candidates have
to be eliminated before someone gets a majority, and that regular WMA
would be better if most of the candidates have to be eliminated before one
gets a majority.

Maybe the reverse symmetric version that you once suggested would be the
best compromise for this context.

Forest

On Sat, 3 Apr 2004, Chris Benham wrote:

> Kevin,
> You  wrote  (Wed.Mar.31):
>
> >A method I would rank between Condorcet and Approval is AER, or "Approval STV."
> >It's IRV, but the elimination order is based on approval.  Because the approval
> >counts don't change, and the elimination order is thus fixed from the beginning,
> >it's monotonic.  It's intuitive, and gives similar results to WV methods.
> >
> To avoid the need for  approval cutoffs, why not use the  plain
>  Weighted Mean Approval scores to set the
> fixed elimination schedule, and then the rest is like fractional  IRV
> with a majority stopping rule ?
>
> Weighted Mean Approval .
> Voters rank the candidates, equal preferences ok.
> Each candidate is given a weight  of  1  for each ballot on which that
> candidate is ranked  alone in first place,  1/2  for each ballot  on
> which that candidate is equal ranked  first with one other candidate,
> 1/3 for each ballot on which that candidate is ranked equal first with
> two other candidates, and so on so that the  total of  all  the weights
> equals  the number of ballots.
> Then  approval scores  for each candidate is  derived  thus: each ballot
> approves all candidates that are ranked in first or equal  first place
> (and does not approve all candidates that are ranked last or equal
> last). Subject to that, if the total weight of the approved candidates
> is less than half  the total of number of ballots, then the candidate/s
> on the second preference-level are also approved, and the third, and so
> on; stopping as soon as  the  total weight of the approved candidates
> equals or exceeds half the total mumber of ballots.
>
> Chris Benham
>
>
>
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```