New Seat Details - Clwyd South and North Montgomeryshire

This page shows the detail of the calculations performed to estimate the general election result for 2017 had the new boundaries for Clwyd South and North Montgomeryshire been in force at that time. The basic idea of the calculation is to look at the district council wards which make up the new seat, and estimate how they voted in 2017. This estimate is based on the recent local election results in those wards, with adjustments made to allow for different turnouts and different voting patterns for local and general elections.

In many cases, wards are divided between several old constituencies or between new constituencies. So the same ward may be shown more than once, but the electorate shown will reflect that ward sub-section.

Election results from a recent local election are given. This is usually the local election closest to 2015 from the period 2012-2015. For multiple-member wards, the votes shown are the sum of the votes cast for all candidates of each party. A negative number indicates candidate(s) elected unopposed.

Calculation method

There are two problems with using the raw (actual) local election results to imply general election results ward-by-ward. Firstly, turnout can be different between local and general elections, which means that the total number of local votes cast does not equal the number of votes cast in each old seat at the general election. To correct for this, we adjust the local votes to match the general election turnout. Each ward's result is scaled, whilst keeping constant the percentage support for each party, so that the total turnout adds up to the old seat's general election turnout. All wards in the old seat are assumed to have the same percentage turnout.

Party	Implied 2017 Votes	Implied 2017 Share
CON	22,173	43.3%
LAB	19,603	38.3%
LIB	4,744	9.3%
Plaid	3,954	7.7%
UKIP	473	0.9%
Green	217	0.4%
CON Majority	2,570	5.0%

Secondly, even though we now have the correct number of votes in the old seat, the party totals will not match the general election result. Some parties do better at the local election than the general election, and others do vice versa. We call these strong and weak parties respectively. The next step is to transfer votes from strong parties to weak parties. This is done by taking votes proportionally away from strong parties and putting them in a transfer pool. For instance if a party got 12,500 local votes, but only 10,000 general election votes, it will lose 20% over all the wards. These votes in each ward will be put in the ward's transfer pool and allocated to the weak parties. Weak parties will get votes transferred to them in proportion to the votes they need over the old seat. For instance, if two weak parties need 4,000 and 1,000 votes respectively, the first party will get 80% of each ward's transfer pool and the second party will get 20% of each ward's transfer pool. The transfer of votes between parties is done using the Electoral Calculus Transition Model.

Clwyd South and North Montgomeryshire: Map

List of old seats forming part of Clwyd South and North Montgomeryshire

Old seat: Clwyd South

The table shows the transfer-adjusted results for each ward in the old seat of Clwyd South, as well as showing which new seat each ward is in.

Old seat: Clwyd South				Transfer-adjusted Results
District	Ward	Electorate 2017	New Seat	CON Votes	LAB Votes	LIB Votes	UKIP Votes	Green Votes	Plaid Votes	MIN Votes	OTH Votes	Total Votes
Denbighshire	Corwen	1,826	Clwyd South and North Montgomeryshire	455	520	19	29	0	192	0	0	1,215
Denbighshire	Llandrillo	930	Clwyd South and North Montgomeryshire	229	243	10	14	0	99	0	0	595
Denbighshire	Llangollen	3,319	Clwyd South and North Montgomeryshire	836	896	41	51	0	314	0	0	2,138
Wrexham	Bronington	2,540	Wrexham	1,039	479	43	26	0	51	0	0	1,638
Wrexham	Brymbo	2,982	Wrexham	1,149	841	23	39	0	75	0	0	2,127
Wrexham	Bryn Cefn	1,482	Wrexham	363	663	36	23	0	47	0	0	1,132
Wrexham	Cefn	3,709	Clwyd South and North Montgomeryshire	884	1,576	43	60	0	106	0	0	2,669
Wrexham	Chirk North	1,811	Clwyd South and North Montgomeryshire	419	766	22	28	0	53	0	0	1,288
Wrexham	Chirk South	1,549	Clwyd South and North Montgomeryshire	374	598	14	22	0	47	0	0	1,055
Wrexham	Coedpoeth	3,482	Wrexham	803	1,282	43	58	0	277	0	0	2,463
Wrexham	Dyffryn Ceiriog / Ceiriog Valley	1,670	Clwyd South and North Montgomeryshire	487	505	16	25	0	99	0	0	1,132
Wrexham	Esclusham	2,023	Wrexham	554	762	27	35	0	73	0	0	1,451
Wrexham	Gwenfro	1,214	Wrexham	227	615	36	18	0	33	0	0	929
Wrexham	Johnstown	2,415	Clwyd South and North Montgomeryshire	660	905	31	43	0	79	0	0	1,718
Wrexham	Llangollen Rural	1,578	Clwyd South and North Montgomeryshire	447	532	16	25	0	56	0	0	1,076
Wrexham	Marchwiel	1,824	Wrexham	606	533	11	25	0	59	0	0	1,234
Wrexham	Minera	1,843	Wrexham	507	678	15	26	0	68	0	0	1,294
Wrexham	New Broughton	2,649	Wrexham	573	1,087	26	39	0	71	0	0	1,796
Wrexham	Overton	2,601	Wrexham	1,097	500	44	28	0	61	0	0	1,730
Wrexham	Pant	1,534	Clwyd South and North Montgomeryshire	395	744	20	26	0	50	0	0	1,235
Wrexham	Penycae	1,479	Clwyd South and North Montgomeryshire	403	659	17	25	0	47	0	0	1,151
Wrexham	Penycae and Ruabon South	1,898	Clwyd South and North Montgomeryshire	532	680	17	27	0	49	0	0	1,305
Wrexham	Plas Madoc	1,198	Clwyd South and North Montgomeryshire	242	733	6	17	0	23	0	0	1,021
Wrexham	Ponciau	3,467	Clwyd South and North Montgomeryshire; Wrexham	869	1,359	131	57	0	109	0	0	2,525
Wrexham	Ruabon	2,071	Clwyd South and North Montgomeryshire	495	848	22	34	0	152	0	0	1,551
	Total	53,094		14,645	19,004	729	800	0	2,290	0	0	37,468

The full details of these calculations are given on the Clwyd South seat details page. Click on "Show workings".

Old seat: Clwyd West

The table shows the transfer-adjusted results for each ward in the old seat of Clwyd West, as well as showing which new seat each ward is in.

Old seat: Clwyd West				Transfer-adjusted Results
District	Ward	Electorate 2017	New Seat	CON Votes	LAB Votes	LIB Votes	UKIP Votes	Green Votes	Plaid Votes	MIN Votes	OTH Votes	Total Votes
Conwy	Abergele Pensarn	1,905	Conwy and Colwyn	491	802	14	0	0	44	0	0	1,351
Conwy	Betws yn Rhos	1,626	Conwy and Colwyn	516	411	13	0	0	222	0	0	1,162
Conwy	Colwyn	3,288	Conwy and Colwyn	1,130	1,039	122	0	0	237	0	0	2,528
Conwy	Eirias	2,749	Conwy and Colwyn	853	824	118	0	0	164	0	0	1,959
Conwy	Gele	3,784	Conwy and Colwyn	1,269	931	34	0	0	304	0	0	2,538
Conwy	Glyn	2,935	Conwy and Colwyn	746	1,220	58	0	0	357	0	0	2,381
Conwy	Kinmel Bay	4,506	Conwy and Colwyn	1,832	1,347	43	0	0	133	0	0	3,355
Conwy	Llanddulas	1,323	Conwy and Colwyn	394	347	52	0	0	50	0	0	843
Conwy	Llandrillo yn Rhos	6,032	Conwy and Colwyn	2,374	1,411	69	0	0	320	0	0	4,174
Conwy	Llangernyw	1,147	Gwynedd	343	281	8	0	0	162	0	0	794
Conwy	Llansannan	1,470	Gwynedd	441	374	11	0	0	207	0	0	1,033
Conwy	Llysfaen	1,862	Conwy and Colwyn	633	763	21	0	0	90	0	0	1,507
Conwy	Mochdre	1,458	Conwy and Colwyn	346	640	16	0	0	59	0	0	1,061
Conwy	Pentre Mawr	2,747	Conwy and Colwyn	1,097	676	79	0	0	86	0	0	1,938
Conwy	Rhiw	4,909	Conwy and Colwyn	1,922	1,312	170	0	0	252	0	0	3,656
Conwy	Towyn	1,842	Conwy and Colwyn	780	472	16	0	0	45	0	0	1,313
Conwy	Uwchaled	1,124	Gwynedd	389	295	10	0	0	71	0	0	765
Denbighshire	Efenechtyd	1,316	Clwyd South and North Montgomeryshire	398	325	14	0	0	179	0	0	916
Denbighshire	Llanarmon-yn-Ial / Llandegla	1,978	Clwyd South and North Montgomeryshire	825	381	23	0	0	99	0	0	1,328
Denbighshire	Llanbedr Dyffryn Clwyd / Llangynhafal	1,218	Clwyd South and North Montgomeryshire	527	210	8	0	0	51	0	0	796
Denbighshire	Llanfair Dyffryn Clwyd / Gwyddelwern	1,793	Clwyd South and North Montgomeryshire	644	470	21	0	0	113	0	0	1,248
Denbighshire	Llanrhaeadr-yng-Nghinmeirch	1,478	Clwyd South and North Montgomeryshire	448	360	12	0	0	204	0	0	1,024
Denbighshire	Ruthin	4,372	Clwyd South and North Montgomeryshire	1,143	1,214	163	0	0	468	0	0	2,988
	Total	56,862		19,541	16,105	1,095	0	0	3,917	0	0	40,658

The full details of these calculations are given on the Clwyd West seat details page. Click on "Show workings".

Old seat: Montgomeryshire

The table shows the transfer-adjusted results for each ward in the old seat of Montgomeryshire, as well as showing which new seat each ward is in.

Old seat: Montgomeryshire				Transfer-adjusted Results
District	Ward	Electorate 2017	New Seat	CON Votes	LAB Votes	LIB Votes	UKIP Votes	Green Votes	Plaid Votes	MIN Votes	OTH Votes	Total Votes
Powys	Banwy	746	Clwyd South and North Montgomeryshire	286	84	129	0	10	36	0	0	545
Powys	Berriew	1,064	Clwyd South and North Montgomeryshire	420	99	174	0	11	49	0	0	753
Powys	Blaen Hafren	1,782	Brecon, Radnor and Montgomery	848	136	220	0	18	66	0	0	1,288
Powys	Caersws	1,712	Brecon, Radnor and Montgomery	720	190	277	0	20	72	0	0	1,279
Powys	Churchstoke	1,214	Brecon, Radnor and Montgomery	373	97	349	0	12	42	0	0	873
Powys	Dolforwyn	1,587	Brecon, Radnor and Montgomery	636	145	227	0	15	59	0	0	1,082
Powys	Forden	1,083	Brecon, Radnor and Montgomery	509	89	150	0	10	34	0	0	792
Powys	Glantwymyn	1,558	Ceredigion and North Pembrokeshire	577	169	268	0	19	82	0	0	1,115
Powys	Guilsfield	1,799	Clwyd South and North Montgomeryshire	688	182	306	0	21	77	0	0	1,274
Powys	Kerry	1,563	Brecon, Radnor and Montgomery	676	140	224	0	15	69	0	0	1,124
Powys	Llanbrynmair	742	Ceredigion and North Pembrokeshire	265	81	116	0	8	31	0	0	501
Powys	Llandinam	1,063	Brecon, Radnor and Montgomery	412	110	182	0	13	52	0	0	769
Powys	Llandrinio	1,656	Clwyd South and North Montgomeryshire	658	173	274	0	16	65	0	0	1,186
Powys	Llandysilio	1,387	Clwyd South and North Montgomeryshire	527	146	225	0	13	50	0	0	961
Powys	Llanfair Caereinion	1,227	Clwyd South and North Montgomeryshire	462	139	312	0	14	60	0	0	987
Powys	Llanfihangel	872	Clwyd South and North Montgomeryshire	337	78	132	0	8	31	0	0	586
Powys	Llanfyllin	1,147	Clwyd South and North Montgomeryshire	500	122	155	0	13	49	0	0	839
Powys	Llanidloes	2,070	Brecon, Radnor and Montgomery	806	277	372	0	29	91	0	0	1,575
Powys	Llanrhaeadr-ym-Mochnant / Llansilin	1,733	Clwyd South and North Montgomeryshire	786	130	210	0	16	77	0	0	1,219
Powys	Llansantffraid	1,511	Clwyd South and North Montgomeryshire	677	124	198	0	14	44	0	0	1,057
Powys	Llanwddyn	818	Clwyd South and North Montgomeryshire	301	86	130	0	9	42	0	0	568
Powys	Machynlleth	1,627	Ceredigion and North Pembrokeshire	546	266	313	0	26	76	0	0	1,227
Powys	Meifod	1,040	Clwyd South and North Montgomeryshire	396	101	161	0	11	50	0	0	719
Powys	Montgomery	1,059	Brecon, Radnor and Montgomery	408	111	179	0	13	42	0	0	753
Powys	Newtown Central	2,103	Brecon, Radnor and Montgomery	996	380	331	0	26	66	0	0	1,799
Powys	Newtown East	1,391	Brecon, Radnor and Montgomery	321	211	438	0	17	139	0	0	1,126
Powys	Newtown Llanllwchaiarn North	1,726	Brecon, Radnor and Montgomery	458	170	532	0	18	58	0	0	1,236
Powys	Newtown Llanllwchaiarn West	1,361	Brecon, Radnor and Montgomery	614	134	188	0	14	40	0	0	990
Powys	Newtown South	1,242	Brecon, Radnor and Montgomery	344	403	233	0	16	40	0	0	1,036
Powys	Rhiwcynon	1,674	Brecon, Radnor and Montgomery	658	171	274	0	17	76	0	0	1,196
Powys	Trewern	1,054	Clwyd South and North Montgomeryshire	450	109	170	0	10	37	0	0	776
Powys	Welshpool Castle	954	Clwyd South and North Montgomeryshire	389	210	201	0	14	45	0	0	859
Powys	Welshpool Gungrog	1,772	Clwyd South and North Montgomeryshire	570	280	614	0	20	64	0	0	1,548
Powys	Welshpool Llanerchyddol	1,652	Clwyd South and North Montgomeryshire	457	201	526	0	17	49	0	0	1,250
	Total	46,989		18,071	5,544	8,790	0	523	1,960	0	0	34,888

The full details of these calculations are given on the Montgomeryshire seat details page. Click on "Show workings".

Old seat: Vale of Clwyd

The table shows the transfer-adjusted results for each ward in the old seat of Vale of Clwyd, as well as showing which new seat each ward is in.

Old seat: Vale of Clwyd				Transfer-adjusted Results
District	Ward	Electorate 2017	New Seat	CON Votes	LAB Votes	LIB Votes	UKIP Votes	Green Votes	Plaid Votes	MIN Votes	OTH Votes	Total Votes
Denbighshire	Bodelwyddan	1,583	Conwy and Colwyn	523	607	13	0	0	34	0	0	1,177
Denbighshire	Denbigh Central	1,567	Clwyd South and North Montgomeryshire	487	538	18	0	0	117	0	0	1,160
Denbighshire	Denbigh Lower	3,575	Clwyd South and North Montgomeryshire	1,132	995	92	0	0	256	0	0	2,475
Denbighshire	Denbigh Upper / Henllan	2,371	Clwyd South and North Montgomeryshire	529	1,073	47	0	0	81	0	0	1,730
Denbighshire	Dyserth	1,905	Rhuddlan and Flint	681	518	36	0	0	44	0	0	1,279
Denbighshire	Llandyrnog	1,652	Clwyd South and North Montgomeryshire	568	458	28	0	0	106	0	0	1,160
Denbighshire	Prestatyn Central	2,814	Rhuddlan and Flint	915	933	25	0	0	43	0	0	1,916
Denbighshire	Prestatyn East	3,219	Rhuddlan and Flint	1,203	939	20	0	0	53	0	0	2,215
Denbighshire	Prestatyn Meliden	1,572	Rhuddlan and Flint	573	502	13	0	0	30	0	0	1,118
Denbighshire	Prestatyn North	4,691	Rhuddlan and Flint	1,306	1,697	44	0	0	48	0	0	3,095
Denbighshire	Prestatyn South West	2,848	Rhuddlan and Flint	862	971	19	0	0	28	0	0	1,880
Denbighshire	Rhuddlan	2,851	Rhuddlan and Flint	1,101	705	46	0	0	123	0	0	1,975
Denbighshire	Rhyl East	3,684	Rhuddlan and Flint	1,034	1,207	25	0	0	29	0	0	2,295
Denbighshire	Rhyl South	2,948	Rhuddlan and Flint	837	1,035	27	0	0	96	0	0	1,995
Denbighshire	Rhyl South East	6,007	Rhuddlan and Flint	1,584	2,305	73	0	0	130	0	0	4,092
Denbighshire	Rhyl South West	3,736	Rhuddlan and Flint	823	2,015	67	0	0	60	0	0	2,965
Denbighshire	Rhyl West	3,367	Rhuddlan and Flint	717	1,543	13	0	0	115	0	0	2,388
Denbighshire	St Asaph East	1,375	Conwy and Colwyn	532	316	31	0	0	32	0	0	911
Denbighshire	St Asaph West	1,265	Conwy and Colwyn	437	431	20	0	0	26	0	0	914
Denbighshire	Trefnant	1,496	Conwy and Colwyn	640	342	5	0	0	70	0	0	1,057
Denbighshire	Tremeirchion	1,313	Conwy and Colwyn	559	294	5	0	0	31	0	0	889
	Total	55,839		17,043	19,424	667	0	0	1,552	0	0	38,686

The full details of these calculations are given on the Vale of Clwyd seat details page. Click on "Show workings".

New seat: Clwyd South and North Montgomeryshire

District	Ward	Electorate 2017	Old Seat	CON Votes	LAB Votes	LIB Votes	UKIP Votes	Green Votes	Plaid Votes	MIN Votes	OTH Votes	Total Votes
New seat: Clwyd South and North Montgomeryshire
Denbighshire	Corwen	1,763	Clwyd South	455	520	19	29	0	192	0	0	1,215
Denbighshire	Denbigh Central	1,706	Vale of Clwyd	487	538	18	0	0	117	0	0	1,160
Denbighshire	Denbigh Lower	3,640	Vale of Clwyd	1,132	995	92	0	0	256	0	0	2,475
Denbighshire	Denbigh Upper / Henllan	2,545	Vale of Clwyd	529	1,073	47	0	0	81	0	0	1,730
Denbighshire	Efenechtyd	1,312	Clwyd West	398	325	14	0	0	179	0	0	916
Denbighshire	Llanarmon-yn-Ial / Llandegla	1,903	Clwyd West	825	381	23	0	0	99	0	0	1,328
Denbighshire	Llanbedr Dyffryn Clwyd / Llangynhafal	1,142	Clwyd West	527	210	8	0	0	51	0	0	796
Denbighshire	Llandrillo	865	Clwyd South	229	243	10	14	0	99	0	0	595
Denbighshire	Llandyrnog	1,707	Vale of Clwyd	568	458	28	0	0	106	0	0	1,160
Denbighshire	Llanfair Dyffryn Clwyd / Gwyddelwern	1,789	Clwyd West	644	470	21	0	0	113	0	0	1,248
Denbighshire	Llangollen	3,099	Clwyd South	836	896	41	51	0	314	0	0	2,138
Denbighshire	Llanrhaeadr-yng-Nghinmeirch	1,469	Clwyd West	448	360	12	0	0	204	0	0	1,024
Denbighshire	Ruthin	4,281	Clwyd West	1,143	1,214	163	0	0	468	0	0	2,988
Powys	Banwy	792	Montgomeryshire	286	84	129	0	10	36	0	0	545
Powys	Berriew	1,096	Montgomeryshire	420	99	174	0	11	49	0	0	753
Powys	Guilsfield	1,854	Montgomeryshire	688	182	306	0	21	77	0	0	1,274
Powys	Llandrinio	1,727	Montgomeryshire	658	173	274	0	16	65	0	0	1,186
Powys	Llandysilio	1,398	Montgomeryshire	527	146	225	0	13	50	0	0	961
Powys	Llanfair Caereinion	1,435	Montgomeryshire	462	139	312	0	14	60	0	0	987
Powys	Llanfihangel	852	Montgomeryshire	337	78	132	0	8	31	0	0	586
Powys	Llanfyllin	1,219	Montgomeryshire	500	122	155	0	13	49	0	0	839
Powys	Llanrhaeadr-ym-Mochnant / Llansilin	1,773	Montgomeryshire	786	130	210	0	16	77	0	0	1,219
Powys	Llansantffraid	1,539	Montgomeryshire	677	124	198	0	14	44	0	0	1,057
Powys	Llanwddyn	825	Montgomeryshire	301	86	130	0	9	42	0	0	568
Powys	Meifod	1,046	Montgomeryshire	396	101	161	0	11	50	0	0	719
Powys	Trewern	1,130	Montgomeryshire	450	109	170	0	10	37	0	0	776
Powys	Welshpool Castle	1,250	Montgomeryshire	389	210	201	0	14	45	0	0	859
Powys	Welshpool Gungrog	2,251	Montgomeryshire	570	280	614	0	20	64	0	0	1,548
Powys	Welshpool Llanerchyddol	1,819	Montgomeryshire	457	201	526	0	17	49	0	0	1,250
Wrexham	Cefn	3,870	Clwyd South	884	1,576	43	60	0	106	0	0	2,669
Wrexham	Chirk North	1,868	Clwyd South	419	766	22	28	0	53	0	0	1,288
Wrexham	Chirk South	1,530	Clwyd South	374	598	14	22	0	47	0	0	1,055
Wrexham	Dyffryn Ceiriog / Ceiriog Valley	1,642	Clwyd South	487	505	16	25	0	99	0	0	1,132
Wrexham	Johnstown	2,491	Clwyd South	660	905	31	43	0	79	0	0	1,718
Wrexham	Llangollen Rural	1,559	Clwyd South	447	532	16	25	0	56	0	0	1,076
Wrexham	Pant	1,790	Clwyd South	395	744	20	26	0	50	0	0	1,235
Wrexham	Penycae	1,670	Clwyd South	403	659	17	25	0	47	0	0	1,151
Wrexham	Penycae and Ruabon South	1,893	Clwyd South	532	680	17	27	0	49	0	0	1,305
Wrexham	Plas Madoc	1,482	Clwyd South	242	733	6	17	0	23	0	0	1,021
Wrexham	Ponciau	2,990	Clwyd South	710	1,110	107	47	0	89	0	0	2,063
Wrexham	Ruabon	2,251	Clwyd South	495	848	22	34	0	152	0	0	1,551
	Total	74,263		22,173	19,603	4,744	473	217	3,954	0	0	51,164

And these are the implied results for 2017 for the new seat of Clwyd South and North Montgomeryshire. Please note that the wards used are those of 2015 in order to be consistent with those used by the Boundary Commissions.

Implied MP at 2017:	Unknown (changed seat) (CON)
County/Area:	Clwyd (Wales)
Electorate:	74,263
Turnout:	68.9%

Clwyd South and North Montgomeryshire: New Boundaries 2018 Calculation

Clwyd South and North Montgomeryshire: Overview

Introduction