Single transferable vote: Difference between revisions
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* Disallowing them, requiring full rankings
* Counting a ballot with N top-ranked candidates as 1/N of a vote for each candidate.
* Giving one vote to each equally
=== Methods of transferring excess votes ===
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=== Deciding the election of the final seat===
The following pseudocode template can be used to run STV with any '''single-winner method''' used to elect the final seat:<blockquote>So long as there are still seats to be filled, and the number of seats remaining to be filled is more than the number of unelected candidates (eliminated or uneliminated) left:
# Count the number of 1st choices for each candidate.
45 L1 > L2 > L3 > C > R2 > R1 ▼
# If any candidate has as many or more votes than the quota, elect them, and spend as much of a quota as possible of their votes. Distribute any surpluses (votes over the quota) that the just-elected candidates had to their voters' next preferences. Repeat until no more candidates can be elected.
'''3. "Un-eliminate" all previously eliminated candidates*, and run any single-winner method, treating ballots with partial weight as partial ballots i.e. a ballot A>B>C with 60% weight remaining in the STV count is treated as 0.6 A>B>C ballots for the single-winner method's count. Elect the winner of the single-winner method.'''
4. Eliminate the candidate with the fewest 1st choices and redistribute their voters' votes to their next preferences. Go to step 2.
The first 4 winners are (L1, L2, R1, R2). If the quota is a Droop quota (17 votes), the remaining ballots will be (ignoring elected candidates):▼
* Conceptually speaking, the candidates who are eliminated during the STV portion of the count could be said to be eliminated from contention for the first N - 1 seats, but still remain in contention for the final seat; though technically, it's possible for the final seat to be filled during the STV count itself (i.e. in a 2-seat election, 2 candidates might each have a quota of 1st choices and automatically win).<ref>https://www.reddit.com/r/EndFPTP/comments/f0muwv/pseudocode_for_stv_with_condorcet_for_the_final/</ref></blockquote>If the single-winner method passes the [[Majority criterion|majority criterion]], then this modification makes STV with Droop quotas become the single-winner method in the single-winner case, since a candidate with a Droop quota of 1st choices is the majority's 1st choice in the single-winner case. If STV with Hare Quotas is used instead, then this modification can be used with any single-winner method that passes [[Pareto criterion|unanimity]] and reduce to that single-winner method in the single-winner case.
5-winner example:<blockquote>45 L1 > L2 > L3 > C > R2 > R1
▲45 R1 > R2 > R3 > C > L2 > L1 </blockquote>The first 4 winners are (L1, L2, R1, R2). If the
10 C > L3
11 R3 > C </blockquote>Standard STV eliminates C and transfers their 10 votes to L3, making L3 the final winner. However, C is the [[Condorcet winner|Condorcet]], [[Bucklin]], and [[Borda]] winner, and would win if any of those methods were used to elect the final seat. Note that electing L3 for the final seat would mean that a 45% minority of voters would have 60% of the seats, whereas with C being elected for the final seat, a majority of voters are guaranteed to have a majority of the seats.
For STV to still pass Droop proportionality with this modification, the single-winner method must pass at least mutual majority (since that is Droop proportionality in the single-winner case). 2-winner example: <blockquote>51 E
19 '''C>A>B'''>D
17 '''B>C>A'''>D
16 '''A>B>C'''>D
17 D>C>A>B
16 D>B>C>A
15 D>A>B>C</blockquote>E has a Droop quota (51 votes) so they win, and their 51 supporters' ballots are spent. Then we run a majority-passing single-winner method, say, [https://en.m.wikipedia.org/wiki/Mutual_majority_criterion#Minimax Minimax] on the remaining 100 ballots, and D wins despite there being a Droop solid coalition and thus a [[Mutual majority criterion|mutual majority]] of 52 voters for (A, B, C). Only a mutual majority-passing single-winner method would guarantee one of A, B, and C wins.
This modification to STV addresses to some extent one of the criticisms made by STV advocates about single-winner methods other than IRV:<blockquote>Furthermore, approval, score, and Condorcet were all designed to be used in single-winner elections only. Ranked choice voting works well for both single-winner ''and'' multi-winner elections. For elections that involve a mixture of single-winner and multi-winner races, we strongly prefer the simplicity of using a uniform voting method across the board.<ref>https://www.fairvote.org/how_is_rcv_better_than_approval_score_or_condorcet_voting_methods</ref></blockquote>{{sectstub}}
=== Related Election Methods ===
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