Equality, Community and Continuity: Reviewing the UK Rules for Constituency Redistributions – Part 2

The review of Parliamentary constituencies that ended prematurely in 2013 would have resulted in most of the 600 seats contested at the 2015 general election being very different from the current 650. In this second blog based on their research Ron Johnston, David Rossiter and Charles Pattie outline why electoral quotas, rather than a reduction in the number of MPs, would be the primary cause of disruption in a boundary review.

The redistributions undertaken by the Boundary Commissions in 2011-2013 were aborted by Parliament for political reasons before their completion, so the 2015 general election will be fought in the current constituencies. But implementation of the 2011 Act was merely delayed until 2016 and a new set of reviews initiated then will, if conducted under the same Rules for Redistributions, be as disruptive to the current map of constituencies as those aborted in 2013. However, this will be primarily due to attempts to introduce electoral quotas, rather than any reduction in the number of MPs.

In seeking to reduce the number of MPs, from 650 to 600, the coalition government was less concerned with the impact on boundaries than in reducing the cost of Parliament.  But as MPs and others saw seats disappear from the map amid the general disruption, the two issues became somewhat conflated.  Surely this reduction had to be part of the cause?  Our research suggests the impact was slight, however.  A few more seats might have escaped change had the number of MPs not been altered, but the causes (and possible solutions) of the major disruption were elsewhere.

The imposition of a single electoral quota plus the reduction in the number of MPs meant that the formerly over-represented parts of the United Kingdom would experience larger decreases in their Parliamentary delegations than others: the number of Welsh MPs would decline from 40 to 30 (a 25 per cent reduction) and Scottish MPs from 59 to 52 (a 12 per cent loss); Northern Ireland’s decline was from 18 to 16 (11 per cent) and England’s from 533 to 502 (6 per cent).

The tight +/-5% tolerance around the UK quota in the 2011 review meant that it was impossible for the Boundary Commissions to allocate constituencies to individual local authorities in many parts of the country; nor was it feasible to leave large numbers of the existing constituencies either unchanged or only minimally changed. So our research asked:

If the maximum allowed variation around the electoral quota were relaxed somewhat, would that give the Commissions greater scope both to reduce the number of constituencies crossing local authority boundaries and to ensure greater continuity in the pattern of constituency representation after reviews, while still ensuring much greater equality in constituency electorates than heretofore – with either 600 or 650 MPs?

We divided the United Kingdom into 75 areas, comprising either single local authorities or groups of neighbouring small authorities, each with electorates averaging 400-800,000. A computer program was developed to identify whether it was possible to construct a substantial number of configurations of constituencies within each of those areas, using wards as the building blocks (in line with the Commissions’ general policy), within a size tolerance ranging from +/-5 to +/-12%, inclusive.

Those analyses for a House of Commons with 600 MPs showed that with a +/-5% tolerance it is not possible to find feasible sets of constituencies in a majority of the 75 areas.  As the tolerance is increased the probability of obtaining such solutions rises quite rapidly at first (at +/-8% tolerance, feasible solutions were identified for 62 of the 75 areas) and then the rate of change declines as fewer areas present a problem.

The analyses of continuity for those solutions showed that regardless of the size tolerance over 35 per cent of the identified constituencies would involve major change from the current set. However, As the size tolerance was relaxed the potential for creating a substantial number of constituencies which differed very little, if at all, from their predecessors increased: the number with no or only minor change increased from 29 per cent for a +/-5% tolerance, to 44 with a +/-10% tolerance.

One reason why there was so much boundary-crossing and so little continuity of representation in the Commissions’ recommendations was because the Boundary Commission for England – unlike the other three – was unwilling to split wards when creating constituencies. Wards have traditionally been used as the building blocks at previous redistributions, but with the tight +/-5% tolerance around the average the Commission found it impossible to create a set of constituencies for many places – especially in London and the large cities; there was either the wrong number of wards or they were too large or both. As a consequence there was much more crossing of boundaries to combine larger and smaller wards in neighbouring authorities than previously, and this meant even less continuity of representation than might otherwise be the case.

These analyses for a House of Commons with 600 MPs were repeated for one with 650 MPs, but retaining a single electoral quota for the whole United Kingdom – which meant that England would gain 14 seats but Scotland, Wales and Northern Ireland would all lose some. The results very largely replicated the earlier findings. Whatever the size of the House of Commons, making electoral equality the paramount criterion applied by the Boundary Commissions meant that disruption to the extent shown in the 2011-2013 exercise was bound to occur – although either or both of relaxing the size tolerance and splitting wards could reduce it to some extent.

We concluded, therefore, that:

  • With a House of Commons comprising 600 MPs, there would be less disruption to the current map of constituencies and a need for fewer constituencies crossing local government boundaries if the tolerance around the electoral quota for individual constituency electorates was relaxed to +/-8%
  • A change in policy on ward-splitting by the Boundary Commission for England would result in a benefit of similar magnitude in terms of continuity but would be less effective in improving the match between Parliamentary constituency and local government boundaries;
  • The greatest benefits would accrue from a relaxed tolerance combined with a more flexible approach to ward-splitting; and
  • With a House of Commons containing 650 MPs similar conclusions apply, though with a marginally better overall match between local authority and Parliamentary constituency boundaries.


That next set of reviews in 2016 will not be able to build on the revised proposals produced by the Commissions in 2012, largely because of uneven population changes across the UK since 2010; already, for example, Scotland is entitled to one more MP than in those recommendations and the south-west of England to one less. Our estimates suggest that both the 2016- review and its successors (the legislation requires redistributions every five years) will be significantly more disruptive than might have been expected and lead us to conclude that:

  • Around one-third of all constituencies are likely to experience major change at each quinquennial review and only about one-third may escape unchanged; and
  • Ward-splitting and a relaxation of the tolerance constraint could reduce the proportion of constituencies experiencing major change at any quinquennial review to below one-fifth and increase those experiencing no change to as much as one-half.

The next scheduled reviews will begin in 2016 and their recommendations submitted to Parliament by October 2018; those constituencies will then be used for the general election scheduled for May 2020. After the 2015 general election, however, there would be time for Parliament to amend the 2011 legislation. If it wished to maintain its principle of greater electoral equality than is currently the case but have less disruption to the constituency map than occurred with the reviews aborted in 2013 it could relax the tolerance around the quota somewhat, or give clearer guidance regarding the use of wards as the building blocks for constituencies (or both). It may also reconsider the size of the House of Commons, but whatever number of MPs is to be elected, removal of the major difference in average constituency electorates across the four UK countries will guarantee considerable disruption from the current map – not only at the next but also at subsequent redistributions.

The full report of this research – Equality, Community and Continuity: Reviewing the UK Rules for Constituency Redistributions – is available on The McDougall Trust website.

Ron Johnston is a professor in the School of Geographical Sciences at the University of Bristol; David Rossiter is a retired Research Fellow who formerly worked at the Universities of Bristol, Leeds, Oxford and Sheffield; and Charles Pattie is a professor in the Department of Geography at the University of Sheffield. They have written together on the Boundary Commissions and constituency definition in the UK since the early 1980s and co-authored The Boundary Commissions: Redrawing the UK’s Map of Parliamentary Constituencies (University of Manchester Press, 1999).

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