New Seat Details - Ogmore and Aberavon

This page shows the detail of the calculations performed to estimate the general election result for 2017 had the new boundaries for Ogmore and Aberavon 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
LAB	34,884	64.7%
CON	12,125	22.5%
Plaid	4,109	7.6%
UKIP	1,944	3.6%
LIB	883	1.6%
LAB Majority	22,759	42.2%

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.

Ogmore and Aberavon: Map

List of old seats forming part of Ogmore and Aberavon

Old seat: Aberavon

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

Old seat: Aberavon				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
Neath Port Talbot	Aberavon	3,887	Ogmore and Aberavon	428	1,891	45	117	0	261	0	0	2,742
Neath Port Talbot	Baglan	5,128	Ogmore and Aberavon	790	2,156	42	148	0	298	0	0	3,434
Neath Port Talbot	Briton Ferry East	2,119	Neath	227	1,035	28	56	0	111	0	0	1,457
Neath Port Talbot	Briton Ferry West	1,977	Neath	221	1,123	17	56	0	94	0	0	1,511
Neath Port Talbot	Bryn and Cwmavon	5,018	Neath	587	2,267	46	130	0	257	0	0	3,287
Neath Port Talbot	Coedffranc Central	2,733	Neath	360	1,284	25	82	0	284	0	0	2,035
Neath Port Talbot	Coedffranc North	1,752	Neath	244	766	55	48	0	102	0	0	1,215
Neath Port Talbot	Coedffranc West	2,629	Neath	300	776	63	51	0	116	0	0	1,306
Neath Port Talbot	Cymmer	2,015	Neath	182	1,087	14	53	0	85	0	0	1,421
Neath Port Talbot	Glyncorrwg	792	Neath	76	404	12	23	0	37	0	0	552
Neath Port Talbot	Gwynfi	895	Neath	85	515	13	27	0	44	0	0	684
Neath Port Talbot	Margam	2,197	Ogmore and Aberavon	416	841	67	61	0	137	0	0	1,522
Neath Port Talbot	Port Talbot	4,052	Ogmore and Aberavon	506	1,899	51	118	0	265	0	0	2,839
Neath Port Talbot	Sandfields East	4,850	Ogmore and Aberavon	618	2,429	41	147	0	272	0	0	3,507
Neath Port Talbot	Sandfields West	4,745	Ogmore and Aberavon	482	2,471	43	134	0	216	0	0	3,346
Neath Port Talbot	Tai-bach	3,557	Ogmore and Aberavon	380	1,717	35	94	0	182	0	0	2,408
	Total	48,346		5,902	22,661	597	1,345	0	2,761	0	0	33,266

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

Old seat: Ogmore

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

Old seat: Ogmore				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
Bridgend	Aberkenfig	1,692	Ogmore and Aberavon	289	494	17	38	0	172	0	0	1,010
Bridgend	Bettws (Ogmore)	1,536	Ogmore and Aberavon	215	815	8	33	0	38	0	0	1,109
Bridgend	Blackmill	1,870	Ogmore and Aberavon	279	857	12	36	0	53	0	0	1,237
Bridgend	Blaengarw	1,260	Ogmore and Aberavon	187	619	17	29	0	40	0	0	892
Bridgend	Bryncethin	995	Ogmore and Aberavon	162	413	26	20	0	44	0	0	665
Bridgend	Bryncoch	1,652	Ogmore and Aberavon	264	738	34	34	0	49	0	0	1,119
Bridgend	Caerau	4,593	Ogmore and Aberavon	726	2,492	29	121	0	117	0	0	3,485
Bridgend	Cefn Cribwr	1,088	Bridgend and Vale of Glamorgan West	186	483	5	23	0	42	0	0	739
Bridgend	Felindre	2,046	Ogmore and Aberavon	402	822	51	43	0	63	0	0	1,381
Bridgend	Hendre	2,985	Ogmore and Aberavon	631	1,243	21	64	0	98	0	0	2,057
Bridgend	Llangeinor	846	Ogmore and Aberavon	151	418	4	19	0	28	0	0	620
Bridgend	Llangynwyd	2,330	Ogmore and Aberavon	445	788	16	54	0	214	0	0	1,517
Bridgend	Maesteg East	3,536	Ogmore and Aberavon	564	1,506	18	84	0	206	0	0	2,378
Bridgend	Maesteg West	4,185	Ogmore and Aberavon	684	1,700	90	100	0	316	0	0	2,890
Bridgend	Nant-y-moel	1,657	Ogmore and Aberavon	297	756	19	42	0	53	0	0	1,167
Bridgend	Ogmore Vale	2,193	Ogmore and Aberavon	394	982	36	54	0	88	0	0	1,554
Bridgend	Penprysg	2,337	Ogmore and Aberavon	443	949	24	49	0	100	0	0	1,565
Bridgend	Pontycymmer	1,648	Ogmore and Aberavon	256	876	19	42	0	52	0	0	1,245
Bridgend	Sarn	1,748	Ogmore and Aberavon	270	840	16	38	0	54	0	0	1,218
Bridgend	Ynysawdre	2,555	Ogmore and Aberavon	460	935	21	57	0	209	0	0	1,682
Rhondda Cynon Taf	Brynna	3,264	Ogmore and Aberavon	522	1,075	18	61	0	228	0	0	1,904
Rhondda Cynon Taf	Gilfach Goch	2,411	Ogmore and Aberavon	366	1,196	48	52	0	62	0	0	1,724
Rhondda Cynon Taf	Llanharan	2,610	Ogmore and Aberavon	498	966	15	55	0	194	0	0	1,728
Rhondda Cynon Taf	Llanharry	2,940	Rhondda and Llantrisant	491	1,070	25	58	0	203	0	0	1,847
Rhondda Cynon Taf	Pont-y-clun	707	Rhondda and Llantrisant	168	190	6	29	0	71	0	0	464
Rhondda Cynon Taf	Talbot Green	12	Rhondda and Llantrisant	2	4	0	0	0	1	0	0	7
	Total	54,696		9,352	23,227	595	1,235	0	2,795	0	0	37,204

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

New seat: Ogmore and Aberavon

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: Ogmore and Aberavon
Bridgend	Aberkenfig	1,538	Ogmore	289	494	17	38	0	172	0	0	1,010
Bridgend	Bettws (Ogmore)	1,689	Ogmore	215	815	8	33	0	38	0	0	1,109
Bridgend	Blackmill	1,882	Ogmore	279	857	12	36	0	53	0	0	1,237
Bridgend	Blaengarw	1,357	Ogmore	187	619	17	29	0	40	0	0	892
Bridgend	Bryncethin	1,012	Ogmore	162	413	26	20	0	44	0	0	665
Bridgend	Bryncoch	1,703	Ogmore	264	738	34	34	0	49	0	0	1,119
Bridgend	Caerau	5,308	Ogmore	726	2,492	29	121	0	117	0	0	3,485
Bridgend	Felindre	2,105	Ogmore	402	822	51	43	0	63	0	0	1,381
Bridgend	Hendre	3,134	Ogmore	631	1,243	21	64	0	98	0	0	2,057
Bridgend	Llangeinor	943	Ogmore	151	418	4	19	0	28	0	0	620
Bridgend	Llangynwyd	2,312	Ogmore	445	788	16	54	0	214	0	0	1,517
Bridgend	Maesteg East	3,622	Ogmore	564	1,506	18	84	0	206	0	0	2,378
Bridgend	Maesteg West	4,402	Ogmore	684	1,700	90	100	0	316	0	0	2,890
Bridgend	Nant-y-moel	1,776	Ogmore	297	756	19	42	0	53	0	0	1,167
Bridgend	Ogmore Vale	2,367	Ogmore	394	982	36	54	0	88	0	0	1,554
Bridgend	Penprysg	2,383	Ogmore	443	949	24	49	0	100	0	0	1,565
Bridgend	Pontycymmer	1,896	Ogmore	256	876	19	42	0	52	0	0	1,245
Bridgend	Sarn	1,854	Ogmore	270	840	16	38	0	54	0	0	1,218
Bridgend	Ynysawdre	2,561	Ogmore	460	935	21	57	0	209	0	0	1,682
Neath Port Talbot	Aberavon	4,114	Aberavon	428	1,891	45	117	0	261	0	0	2,742
Neath Port Talbot	Baglan	5,150	Aberavon	790	2,156	42	148	0	298	0	0	3,434
Neath Port Talbot	Margam	2,284	Aberavon	416	841	67	61	0	137	0	0	1,522
Neath Port Talbot	Port Talbot	4,257	Aberavon	506	1,899	51	118	0	265	0	0	2,839
Neath Port Talbot	Sandfields East	5,258	Aberavon	618	2,429	41	147	0	272	0	0	3,507
Neath Port Talbot	Sandfields West	5,018	Aberavon	482	2,471	43	134	0	216	0	0	3,346
Neath Port Talbot	Tai-bach	3,611	Aberavon	380	1,717	35	94	0	182	0	0	2,408
Rhondda Cynon Taf	Brynna	2,901	Ogmore	522	1,075	18	61	0	228	0	0	1,904
Rhondda Cynon Taf	Gilfach Goch	2,625	Ogmore	366	1,196	48	52	0	62	0	0	1,724
Rhondda Cynon Taf	Llanharan	2,632	Ogmore	498	966	15	55	0	194	0	0	1,728
	Total	81,694		12,125	34,884	883	1,944	0	4,109	0	0	53,945

And these are the implied results for 2017 for the new seat of Ogmore and Aberavon. 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:	Chris Elmore (LAB)
County/Area:	Mid Glamorgan (Wales)
Electorate:	81,694
Turnout:	66.0%

Ogmore and Aberavon: New Boundaries 2018 Calculation

Ogmore and Aberavon: Overview

Introduction