[EM] Re: Approval STV
Chris Benham
chrisbenham at bigpond.com
Fri Apr 2 16:14:03 PST 2004
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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