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Voting matters - To advance the understanding of preferential voting
Issue 24, October 2007
(Complete issue in PDF, 496Kb.)
The McDougall Trustees recently asked a senior academic is undertake a
review of Voting matters, partly due to some comments on the Internet.
You may have noticed a difference to the front sheet since the
subtitle has been changed from the previous text: for the technical
issues of STV. This change reflects the actual content which is not
restricted to STV.
An issue which arose from the review was a criticism of the paper by
Allard in Issue 5 which gives a low figure for the number of STV
elections which are non-monotonic. It is perhaps not obvious that an
election can fail to be monotonic in two distinct ways. Given an
election for three seats and six candidates in which A, B and C are
elected and X, Y and Z fail to be elected, then increased support for
C could result in C not being elected; or alternatively, reduced
support for X could result in X being elected. It seems clear that a
more robust estimate for the occurrence of a non-monotonic election is
needed. An academic has agreed to investigate this. It would also be
interesting to know if the actual STV counting rule had an impact on
There are 4 papers in this issue, all of which are comments or reviews of other
The Editor must correct a statement made in the last editorial which
stated: In electoral terms, Meek has the advantage that the
intervention of a no-hope candidate cannot change the choice of the
elected candidates - a failing of all the rules used for current
hand-counting STV methods. This is not correct in general. For
instance, if a Meek count excludes candidates A, B and C (in that order), then
rerunning the count without A will get the same result, and
also without A and B, or A, B and C. However, a different result may
be obtained by excluding B (without A), or by excluding A and C
without B, etc. With a conventional count, if the first stage excludes
a candidate, then rerunning the count without that candidate does not
necessarily obtain the same result.
Readers are no doubt familiar with the problems that were encountered
with the Scottish elections this spring. However, the STV elections
went off smoothly. The Glasgow election area provided complete
details of the voting profiles on the Internet, although it was
the only area to do so. This provides a very significant addition
to the STV data available for academic study.
The site www.votingmatters.org.uk is now working on the Internet,
but bookmarks to the old site should be changed to the new one, since
the old site will be removed eventually.
- I D Hill: STV in Northern Ireland and proportional representation
This paper makes two suggestions for increasing the degree of
proportionality for elections. Changing the number of seats per
constituency would require a legislative change, but is conceptually
simple. Using the eligible votes to determine the split is
more radical, but why not? What do readers think of this?
- Jonathan Lundell and I D Hill: Notes on the Droop quota
The Droop quota is a key issue of STV. Note that the authors place great
emphasis on DPC (see the paper for details). This criterion could be
regarded as critical for STV, yet some counting methods fail this test,
at least in marginal situations.
- H R Droop: On Methods of Electing Representatives
In preparing the previous paper, it was clear that the original
paper of Droop was not widely available. Hence it was decided to
reprint it, with the approval of the original publisher (although
long out of copyright). Although long by modern standards, it
raises very many issues, the majority of which are still
outstanding today. Thanks to the two previous authors and David
Farrell in assisting with this reprinting.
- E Stensholt: Review - Elections in split societies
This is a review of a book edited by Peter Emerson. The topic of the
book is voting systems based upon Borda scores. Such systems are
clearly related to STV in many respects and hence a comparison is
surely of interest. In order to present the review, a scheme for
illustrating voting profiles is used. Note that the review and
the book takes into account the political position of a divided society
in Northern Ireland.
Readers are reminded that views expressed in Voting matters by
contributors do not necessarily reflect those of the McDougall Trust
or its trustees.
Papers with citations
- David Hill: STV in Northern Ireland. (p1-2, PDF 92Kb)
- Jonathan Lundell and I D Hill: Notes on the Droop quota. (p3-6, PDF 200Kb)
- H R Droop: On Methods of Electing Representatives. (p7-46, PDF 1.1Mbb)
- E Stensholt: Review Ñ Elections in split societies. (p47-56, PDF 396Kb)