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Voting matters - Issue 7, September 1996

Equality of preference - an alternative view

I D Hill

In the preceding paper, Hugh Warren states 'Hence Black's concern is justified', but the example from which he derives this opinion is not convincing. It really concerns the question of how a tie is to be resolved, since in each of his three cases the AB supporters have 7.5 votes and the EF supporters have 7.5 votes. This makes it critically dependent on using a version of STV in which the quota is defined to give precisely 7.5 as in Newland and Britton, second edition and not 7.5 plus a minimal amount as in most versions of STV, such as Newland and Britton, first edition, for example. It also depends on the rule that anyone reaching the quota is to be deemed elected at once even though some other candidate could catch up if the process were continued.

I am not objecting to those features, but if we are prepared to base conclusions on examples that depend critically on them, it is easy enough to construct one that points to the opposite conclusion. Consider 4 candidates for 3 seats with an odd number, n, of voters who support A and B, and an equal number, n, who support C and D. The quota will be n/2 and if the AB party do not use equality, no matter how they arrange their votes between saying AB and saying BA, one of their candidates will have more than a quota, and the other less than a quota, on the first count. If the CD party all put C and D as equal first, each of their candidates will have exactly a quota on the first count and consequently either ACD or BCD will be elected.

It follows that Black's concern is not justified. In these extreme cases use of equality could either harm or help and it is not possible to know which. In reality such extreme cases rarely, if ever, occur. What would normally happen if equality were used would be for one of the two candidates to go out (either as excluded or elected) at some stage and then the relevant part of the vote would be transferred to the other candidate, so nothing would be lost.

References

  1. C H E Warren. STV and Equality of Preference. Voting matters, Issue 7, p6, September 1996.
  2. R A Newland and F S Britton. How to conduct an election by the Single Transferable Vote, second edition, ERS, 1976.
  3. R A Newland and F S Britton. How to conduct an election by the Single Transferable Vote, first edition, ERS, 1973.
Up: Issue 7 Previous: Paper 5