Yes, this works. One downside is that, unlike STV, a hand count becomes quite untractable.
Jameson 2012/2/2 Raph Frank <[email protected]> > One possible way of combining AV + STV is to allow equal ranks. This > method becomes a method that is very similar to approval in the single > winner case. > > When determining if a candidate is elected, all candidates at the rank > share the remaining vote strength, but when determining if a candidate > should be eliminated, the candidates at the rank get the full strength > of the ballot, like in approval. > > A feature of STV is that the proportionality for solid coalitions > criterion isn't affected by the elimination ordering, so you can use > any rule that you want. This assumes that candidates who exceed the > quota are elected (and elected candidates are immune from > elimination). > > Assuming there was a ballot: > > A: 1 > B: 1 > C: 2 > D: 2 > E: 3 > F: 3 > > In round 1, the ballot would count as > > For electing: > A: 0.5 > B: 0.5 > Others: 0 > > For eliminating > A: 1 > B: 1 > Others: 0 > > So, the vote is shared when determining if someone has reached the > quota, but is full strength when determining who to eliminate. > > If a candidate has more than a quota of "electing" votes, he is deemed > elected. Otherwise, the candidate with the lowest "eliminating" > votes is eliminated. > > If B was eliminated and A was elected with 133.3% of the quota (so 75% > of the voting strength consumed), then the ballot would count as: > > For electing: > A: 0.75 > B: 0 (eliminated) > C: 0.125 > D: 0.125 > > To eliminate > A: 0.75 (irrelevant since already elected) > B: 0.75 (irrelevant since already eliminated) > C: 0.25 > D: 0.25 > Others: 0 > > This means that if all party supporters vote for party members as > ranks 1 and 2, then the party is guaranteed to gets its share of the > seats. This follows from the solid coalition criterion. > > However, when determining the intra-party ordering, rank 1 candidates > are considered approved and rank 2 candidates are disapproved. The > most approved party candidates (up to the limited number of seats the > party gets) are the last to be eliminated, so they will be the ones > elected. > > Standard PR-STV becomes IRV in the single seat case. However, this > system becomes a method that is very similar to approval in the single > seat case. > > This means that for parties that get 1 seat, the intra-party decision > is made by IRV, but with this method, the intra-party decision is made > by approval (or at least an approval-like method). > > Assuming Meek's method for the transfers, then the rules are > > For both vote types (for election and for elimination) > > Vote strength passed to the next rank > > - the amount that would be passed to the next rank if all candidates > at the current rank were ranked in order > - This is the product of (1 - keep factor) for all candidates at the > current rank times the vote passed into this rank > - Nothing is passed to the next rank unless all candidates at the > current rank are elected or eliminated > > Sharing (for election) > > - vote strength not passed to the next rank is shared between > candidates at the current rank in proportion to their keep factors > > Sharing (for elimination) > > - vote strength not passed to the next rank is given at full strength > to all candidates at the current rank > ---- > Election-Methods mailing list - see http://electorama.com/em for list info >
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