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Voting matters - Issue 7, September 1996

How was my vote used?

I D Hill

If an election has been conducted by STV using Meek counting, and the final keep values have been published (as I think that they should be), any voters who remember their preference orders can work out how their votes were used, as follows.

Suppose you voted for Bodkins as first preference, for Edkins as second preference, etc., where their final keep values were published as 0.310, 0.772, etc., as shown in the table below. The first thing to do is to make such a table with the order of preference that you actually used for the real candidates and fill in their published final keep values in column (3).

Always start with 1.000 as the first item, one line above your first candidate, in column (6), and then in each row in turn, fill in columns (4), (5) and (6) using the rules shown.

When an excluded candidate appears, such as Atkins above, the keep value is 0.000, so no part of the vote is kept. When a candidate was either the runner-up or the last to be elected, such as Firkins, the keep value is 1.000, so that candidate keeps everything received and later preferences get nothing.

Column (5) tells how the vote was used. 0.310 of it went to help elect Bodkins, 0.533 of it went to help elect Edkins, 0.110 of it went to help elect Dawkins and the remaining 0.047 went to Firkins and, if Firkins was runner-up, was unused.

I have been asked by someone who has seen the above to produce something similar for traditional-style STV (and, in particular, for Newland and Britton rules, second edition). Having had a look at the problem, I have concluded that, for anyone who really understands what is going on, the information can be derived from the result sheet in an ad hoc way, but that it is not possible to do anything as general, or as simple, as the above.

This should be offered as an exercise for those who think the traditional rules simpler than the Meek rules. Let them do it. I do not deny, of course, that the traditional rules are less long-winded for making a hand-count, but in every other way, in principle and in practice, the Meek rules are much the simpler.

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