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 2019 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

PartyOld SeatsNew SeatsChangeDisappearSwitch OutSwitch InFresh

The table shows how the various changes affect each party in this area. 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: Alyn and Deeside; Carmarthen East and Dinefwr; Ynys Mon.

The new seats which are gained from another party are: Alyn and Deeside; Carmarthen; Anglesey and Bangor.


New seatPrimary componentSecondary component(s)
Alyn and Deeside 100% of Alyn and Deeside 31.5% of Delyn
Clwyd South and North Montgomeryshire 56.2% of Clwyd South 43.5% of Montgomeryshire
21.4% of Clwyd West
16.4% of Vale of Clwyd
Conwy and Colwyn 72.0% of Clwyd West 67.1% of Aberconwy
12.6% of Vale of Clwyd
Rhuddlan and Flint 71.0% of Vale of Clwyd 68.5% of Delyn
Wrexham 100% of Wrexham 43.8% of Clwyd South


New seatPrimary componentSecondary component(s)
Carmarthen 92.4% of Carmarthen East and Dinefwr 40.8% of Carmarthen West and Pembrokeshire South
Ceredigion and North Pembrokeshire 100% of Ceredigion 23.8% of Preseli Pembrokeshire
7.6% of Carmarthen East and Dinefwr
8.4% of Montgomeryshire
Llanelli 100% of Llanelli 32.0% of Gower
Pembrokeshire Mid and South 76.2% 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)
Anglesey and Bangor 100% of Ynys Mon 42.5% of Arfon
13.8% of Aberconwy
Gwynedd 100% of Dwyfor Meirionnydd 57.5% of Arfon
19.2% of Aberconwy
6.6% of Clwyd West

Mid Glamorgan

New seatPrimary componentSecondary component(s)
Bridgend and Vale of Glamorgan West 100% of Bridgend 20.2% of Vale of Glamorgan
2.0% of Ogmore
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 Aberavon 91.3% of Ogmore 58.8% of Aberavon
Rhondda and Llantrisant 100% of Rhondda 45.2% of Pontypridd
6.7% of Ogmore


New seatPrimary componentSecondary component(s)
Brecon, Radnor and Montgomery 100% of Brecon and Radnorshire 48.2% of Montgomeryshire

South Glamorgan

New seatPrimary componentSecondary component(s)
Cardiff North 93.6% of Cardiff North 37.6% of Cardiff Central
0.2% of Cardiff South and Penarth
Cardiff South and East 54.2% of Cardiff South and Penarth 62.4% of Cardiff Central
6.4% of Cardiff North
Cardiff West 100% of Cardiff West 16.1% of Cardiff South and Penarth
4.8% of Pontypridd
Vale of Glamorgan East 79.8% of Vale of Glamorgan 29.5% of Cardiff South and Penarth

West Glamorgan

New seatPrimary componentSecondary component(s)
Gower and Swansea West 82.9% of Swansea West 46.0% of Gower
10.6% of Swansea East
Neath 100% of Neath 41.2% of Aberavon
Swansea East 89.4% of Swansea East 22.0% of Gower
17.1% of Swansea West