Back when people considered such things, they had a problem with STV's arbitrary rule to eliminate the least-popular candidate during the vote counts. They said that no one could know that the least-popular candidate, if allowed to stay in the running, would not collect many votes through transfers from other candidates and accumulate votes as per back-up preferences on ballots originally going to other candidates. This may be true but under STV, some candidates must be eliminated to narrow the field and if not on the criterion of relative popularity, then on what basis would the candidates be chosen for elimination?
It may be arbitrary. But it is no more arbitrary than the First past the post's arbitrary rule to declare elected the leading candidate whether he or she had received a majority of the votes or not. The leader is awarded the seat even if vote transfers might have allowed someone else to get more votes and be elected.
And note that STV's arbitrary rule does not in every case determine who will be the winning candidate. In some instances the winning candidate is not determined by the elimination of others but by his or her own popularity among voters.
First, here is a sample of being elected by surviving eliminations.
Election by being among few remaining candidates after elimination
Take the case where four candidates are running for two seats, with 100 votes still in play. Quota is 33 votes.
(This case also applies to instances where the field of candidates, once 9 or seven or some other large number, has been reduced to four with only two seats remaining open.)
first count second count
Candidate votes transfers totals
E 30 2 32
F 26 2 28
G 24 5 29
H 20 -20 0
Exhausted votes 11 11
Total votes 100 100
in the next count, the least-popular candidate. "F," is eliminated.
This leaves only three remaining candidates and two open seats,
E and G are declared elected because they are the last remaining when the number of candidates has dropped to the number of open seats (or actually by being the leading candidates when there is only one more candidate than the number of open seats.)
In this case, it is said that E and G were elected with partial quotas.
The only votes wasted in cases like these are those belonging to the final candidate eliminated (F in this case) and the exhausted votes. And in fact some of F's votes if they had been transferred might have gone to E and G anyway.
Then we look at cases where survivors of eliminations are not all declared elected.
Election by quota
Take the case where there are five candidates still in the running for two seats, with 100 votes still in play. Quota is 30 votes.
(This case applies to instances where the field of candidates, once 9 or seven or some other large number, has been reduced to five with only two seats remaining open.)
first count second count
Candidate votes transfers totals
A 28 2 30
B 27 1 28
C 26 4 30
D 10 1 11
E 9 -9 0
Exhausted votes 1 1
Total votes 100 100
A and C are declared elected because their vote totals equalled or exceeded quota.
In the second case the elimination of the least-popular candidate did not determine the election of any two specific candidates. Any two of A, B, C or D might have been elected eventually in a later count. Achieving quota (a mark pre-set much earlier) in this count determined that A and C would take the last seats.
In this case, it is said that E and G were elected with partial quotas.
Wasted votes are those not used to elect the winner.
Votes wasted in cases like these are those belonging to the "middle" candidates who were neither eliminated nor elected (B and D in this case), and the exhausted votes. Thus wastage in these cases is larger than under election by partial quotas (above). But likely at least some of B's and D's votes if they had been transferred might have gone to A and C anyway.
STV's arbitrary rule forcing elimination of the least-popular candidates thus determines those who are definitely out of the running but does not in all cases determine the winner.
This is unlike FPTP's arbitrary rule of naming the leading candidate as the winner by looking at his or her simple lead over the nearest contender no matter how slim and no matter how few votes (how small a percentage of the vote) that leader has.
Guess which one I find more fair!
Thanks for reading.
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