[EM] approval and PR-STV

raphfrk at netscape.net raphfrk at netscape.net
Tue Jan 30 14:58:22 PST 2007

``` Has this every been proposed as a way to mix approval and PR-STV ?

It is like IRV with equal weights, so I am assuming that it has been proposed. It is also similar to sequential proportional approval voting, just that the ballot re-weighting calculation is different.

It is equivalent to PR-STV if no voter votes equal ranks.

Ballots are ranked ballots with equal ranks allowed.

Process:

1) Set each ballot to weight 1.0

2) Quota = (Totals Ballots)/(1+Seats)

3) A ballot counts as voting for a candidate if the candidate is in the highest rank that has at least 1 candidate that is still unelected and uneliminated

4) Total the weights of all the ballots voting for each candidate

5) If the total for the candidate with the highest total exceeds the quota:
Deem that candidate elected
Multiply the weight of all the ballots that vote for the candidate by
(Candidate's total - Quota)/(Quota)]

Otherwise,
Eliminate the candidate with the fewest votes

6) Goto 3) until the number of uneliminated candidates is less than or equal to the number of seats

7) Deem any remaining candidate who has not been eliminated as elected.

Current PR-STV effectively implements IRV for the intra "faction" election.

If there is 5 seats and a faction represents 20% of the electorate, the members of the faction can gaurentee that a candidate from the faction takes the seat. However, that is not necessarily the best candidate from the faction.

Assuming that 3 candidates from the faction run:

L>C>R>>(rest of the candidates): 8%
C>L>R>>(rest of the candidates): 2%
C>R>L>>(rest of the candidates): 2%
R>C>L>>(rest of the candidates): 8%
(rest of the candidates)>>(L,R,C): 80%

Ignoring the effects of transfers into the faction, C will be eliminated before R and L and then they will tie.

However, C is the condorcet winner for the faction.

Under the equal ranks proposal. It is likely that C will get some approvals from L and R supporters. If half of each approve both C and their favourite, then C will get 10% first choices. This will mean that either L or R will be eliminated first and all the votes will transfer to C.

Raphfrk
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Interesting site
"what if anyone could modify the laws"

www.wikocracy.com
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