The Boundary Commissions for Scotland and Wales have published proposals for changes to constituency boundaries, which will be finalised in 2023.

Following our analysis of proposed new constituencies in England, this Insight looks at the revised proposals for Scotland and Wales.

Both Scotland and Wales are set to lose seats in the 2023 boundary review – Scotland will have 57 Westminster constituencies, down from 59, while Wales will have 32, down from 40. The new boundaries will not be used until the next general election after July 2023.

What are boundary reviews?

Constituency boundaries are reviewed periodically to make sure constituencies all have roughly the same number of voters and . The reviews alter boundaries to reflect rising and falling populations, as well as changes in ward boundaries.

For more on the reviews see our briefings on boundary reviews, public consultations, and next steps following the revised proposals.

How would Scotland change?

Under the proposals, 11 constituencies in Scotland would have unchanged boundaries (including two protected island constituencies).

The remaining constituencies would all change in some way and may be split between more than one successor constituency. For nine seats, the closest replacement would be less than 60% similar to the existing constituency.

The table below shows the percentage of change between the consistency in its current form and its proposed successor.

Boundary review Scotland: change in exsisting constituencies
Population and premises-based analysis, by party
Similarity between current constituency and closest successor Number of seats Proportion of seats
Unchanged 11 19%
Over 95% 3 5%
90-95% 7 12%
80%-90% 13 22%
70-80% 7 12%
60-70% 9 15%
50-60% 7 12%
40-50% 1 2%
Under 40% 1 2%
Total Seats 59 100%

The current Glasgow Central constituency would be divided up between five successor constituencies. In the proposals, it contributes 45% of its population to the new Glasgow South West constituency, and smaller proportions to four other surrounding constituencies.

Glasgow-central-labels: Map showing how the current Glasgow Central constituency would be split between five surrounding successor constituencies.

Ross, Skye and Lochaber would also change substantially – this single constituency would contribute 50% of its population to the new Inverness-shire and Wester Ross constituency, 42% to Caithness, Sutherland and Easter Ross, and the remainder to Argyll, Bute and South Lochaber.

There are a number of boundary changes to align constituency boundaries with ward boundaries that do not affect any residential premises – most notably near Talla Water in Scottish Borders.

How would Wales change?

Because the number of seats in Wales will be 20% lower after this boundary review, the proposed changes are significant in most parts of the country. Only one constituency is unchanged (the protected island seat of Ynys Môn) and only one would be shrunk (Vale of Glamorgan).

Under the proposals, 18 of the 40 current constituencies would have a closest successor that is very different from the current constituency (with a similarity rating below 60%).

The table below shows how much the current constituencies would be similar or different to the proposed successor.

Boundry review Wales: change in existing constituencies Population and premises-based analyysis, by party

Boundary review Wales: change in existing constituencies
Population and premises-based analysis, by party
Similarity between current constituency and closest successor Number of Seats Proportion of Seats
Unchanged 1 2.5%
Over 95% 1 2.5%
90%-95% 2 5.0%
80%-90% 5 12.5%
70%-80% 5 12.5%
60%-70% 8 20.0%
50%-60% 9 22.5%
40%-50% 7 17.5%
Under 40% 2 5.0%
Total Seats 40 100%

Thirteen proposed constituencies would be bigger versions of their current form – that is, they would contain all the area of the existing constituency and also acquire new areas. For instance, the current Aberavon constituency would be wholly contained in the new Aberafan Porthcawl constituency. Aberavon makes up 69% of the population of the new constituency, with the remainder coming from parts of the existing Bridgend constituency.

Swansea West would be the most changed constituency in Wales. It contributes 51% of its current population to the new Gower and Swansea West constituency, 49% to Swansea Central and North, and a very small proportion to Neath and Swansea East. This is shown on the map below. Note that the boundaries shown include tidal areas beyond the coastline.

Swansea-west-labels: Map showing how the current Swansea West constituency would be split between three surrounding successor constituencies.

Clwyd South would also have major changes. It would contribute 53% of its population to the new Montgomeryshire and Glyndwr constituency, 39% to Wrexham, and 9% to Clwyd East, as shown in the map below.

Clywd-south-labels: Map showing how the current Clwyd South constituency would be split between three surrounding successor constituencies.

Mapping the changes

The maps below show how much existing constituencies would change in Wales and Scotland. Darker shading indicates more change between the current constituency and its closest successor.

Scotland_wales_preservation: two maps showing similarity between each existing constituency in Scotland and Wales and their closest successors. Information for each constituency can be found in the downloadable data file.

Constituencies covering large geographical areas

The UK’s largest constituencies by geographical area are in Scotland and Wales, because they contain the areas with the sparsest populations. Since the number of constituencies in Scotland and Wales will fall, the average constituency area in those countries will grow.

Despite this, the largest proposed constituency in the UK – Inverness-shire and Wester Ross (11,064 km2) – would be smaller than the current largest constituency (Ross, Skye and Lochaber, 12,769 km2).

But other constituencies would grow – even some that are proposed to keep the same name.

The proposed Wrexham constituency covers nearly three times the area of the existing constituency, and the proposed Bridgend would be more than double the area of the current Bridgend. In Scotland, Caithness, Sutherland and Easter Ross constituency would grow by over 1,600 km2 – an area larger than all but eight English constituencies.

The biggest constituencies have large distances and long travel times between towns and villages within them. In the proposed Inverness-shire and Wester Ross constituency, travelling between Tomatin and Glendale is 146 miles by road (around three and a half hours to drive). In Argyll, Bute and South Lochaber, it’s 119 miles by road from Campbeltown to Corran (just over three hours). In Wales, a long route would be in Ceredigion Preseli, where driving from Croesgoch to Eglwys Fach would be 78 miles (over two hours).

Download the data

More detail on individual constituencies is included in the spreadsheet that can be downloaded below. For each constituency, it shows how much of the current seat would be contained within its successor, and how much of the successor would be made up of the current constituency.

 Download data in Excel 

About the data

  • For a description of the calculation used here and a comparison with other options,  see the “about the data” section of our Insight on English boundaries.

About the authors: Carl Baker is a statistician specialising in health and geography at the House of Commons Library. Elise Uberoi is a statistician specialising in elections and Parliament at the House of Commons Library.

Photo by Benjamin Elliott on Unsplash

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