Wales: New Constituency Boundaries 2018

Each new seat can be described as a combination of parts of old seats. These tables show this decomposition. The winner of the old seat at the 2017 election is shown by party colour, as is the implied winner of the new seat.

The implied results are calculated using the local election results for the wards which make up each old seat. This should give the most accurate projection, since it reflects varying political behaviour across the seat.

Wales Change Table

  Old SeatsNew SeatsChangeDisappearSwitch OutSwitch InFresh

The table shows how the various changes affect each party in this region. The total old and new seats are shown for each party, as well as their difference ('Change'). The change in seats is also explained through the four explanations:

The old seats which are disappearing are: Aberavon; Aberconwy; Arfon; Cardiff Central; Carmarthen West and Pembrokeshire South; Delyn; Gower; Islwyn; Montgomeryshire; Newport East; Pontypridd.

The old seats which are lost to another party are: Carmarthen East and Dinefwr; Clwyd South; Dwyfor Meirionnydd; Vale of Glamorgan.

The new seats which are gained from another party are: Carmarthenshire; Clwyd South and Montgomeryshire North; Clwyd North and Gwynedd; Vale of Glamorgan East.


New seatPrimary componentSecondary component(s)
Alyn and Deeside 100% of Alyn and Deeside 30.8% of Delyn
Clwyd South and Montgomeryshire North 56.2% of Clwyd South 49.6% of Montgomeryshire
23.4% of Clwyd West
7.2% of Dwyfor Meirionnydd
3.0% of Vale of Clwyd
Colwyn and Conwy 69.2% of Clwyd West 80.8% of Aberconwy
Flint and Rhuddlan 71.0% of Vale of Clwyd 69.2% of Delyn
Wrexham Maelor 100% of Wrexham 43.8% of Clwyd South


New seatPrimary componentSecondary component(s)
Carmarthenshire 92.4% of Carmarthen East and Dinefwr 40.8% of Carmarthen West and Pembrokeshire South
Ceredigion and North Pembrokeshire 100% of Ceredigion 24.0% of Preseli Pembrokeshire
7.6% of Carmarthen East and Dinefwr
8.2% of Montgomeryshire
Llanelli and Lliw 100% of Llanelli 32.8% of Gower
Pembrokeshire South 76.0% of Preseli Pembrokeshire 59.2% of Carmarthen West and Pembrokeshire South


New seatPrimary componentSecondary component(s)
Blaenau Gwent 100% of Blaenau Gwent 48.8% of Islwyn
Caerphilly 63.9% of Caerphilly 46.5% of Islwyn
20.7% of Newport West
Monmouthshire 87.9% of Monmouth 35.9% of Newport East
Newport 68.9% of Newport West 64.1% of Newport East
Torfaen 100% of Torfaen 12.1% of Monmouth
10.3% of Newport West


New seatPrimary componentSecondary component(s)
Clwyd North and Gwynedd 92.8% of Dwyfor Meirionnydd 26.0% of Vale of Clwyd
25.4% of Arfon
19.2% of Aberconwy
7.5% of Clwyd West
Ynys Mon and Arfon 100% of Ynys Mon 74.6% of Arfon

Mid Glamorgan

New seatPrimary componentSecondary component(s)
Bridgend and Vale of Glamorgan West 100% of Bridgend 20.2% of Vale of Glamorgan
Cynon Valley and Pontypridd 100% of Cynon Valley 50.0% of Pontypridd
Merthyr Tydfil and Rhymney 100% of Merthyr Tydfil and Rhymney 36.1% of Caerphilly
4.7% of Islwyn
Ogmore and Port Talbot 100% of Ogmore 38.3% of Aberavon
Rhondda and Llantrisant 100% of Rhondda 45.1% of Pontypridd


New seatPrimary componentSecondary component(s)
Brecon, Radnor and Montgomery 100% of Brecon and Radnorshire 42.2% of Montgomeryshire

South Glamorgan

New seatPrimary componentSecondary component(s)
Cardiff North 89.0% of Cardiff North 37.6% of Cardiff Central
4.8% of Pontypridd
Cardiff South and East 54.3% of Cardiff South and Penarth 62.4% of Cardiff Central
11.0% of Cardiff North
Cardiff West 100% of Cardiff West 16.1% of Cardiff South and Penarth
Vale of Glamorgan East 79.8% of Vale of Glamorgan 29.6% of Cardiff South and Penarth

West Glamorgan

New seatPrimary componentSecondary component(s)
Gower and Swansea West 83.1% of Swansea West 57.9% of Gower
Neath and Aberavon 100% of Neath 47.0% of Aberavon
Swansea East 100% of Swansea East 16.9% of Swansea West
14.7% of Aberavon
9.3% of Gower