New Seat Details - Swindon South

This page shows the detail of the calculations performed to estimate the general election result for 2017 had the new boundaries for Swindon South 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	25,486	48.1%
LAB	23,246	43.9%
LIB	2,144	4.0%
UKIP	1,345	2.5%
Green	783	1.5%
CON Majority	2,240	4.2%

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.

Swindon South: Map

List of old seats forming part of Swindon South

Old seat: Swindon North

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

Old seat: Swindon North				Transfer-adjusted Results
District	Ward	Electorate 2017	New Seat	CON Votes	LAB Votes	LIB Votes	UKIP Votes	Green Votes	NAT Votes	MIN Votes	OTH Votes	Total Votes
Swindon	Blunsdon and Highworth	8,634	Swindon North	3,413	1,702	149	146	85	0	0	0	5,495
Swindon	Covingham and Dorcan	6,766	Swindon North	2,451	1,604	216	136	64	0	0	0	4,471
Swindon	Gorse Hill and Pinehurst	8,209	Swindon North	2,634	3,131	228	191	110	0	0	0	6,294
Swindon	Haydon Wick	8,779	Swindon North	3,579	2,056	212	172	92	0	0	0	6,111
Swindon	Mannington and Western	3,772	Swindon South	1,286	1,326	100	84	50	0	0	0	2,846
Swindon	Penhill and Upper Stratton	9,100	Swindon North	2,793	3,046	192	186	102	0	0	0	6,319
Swindon	Priory Vale	7,986	Swindon North	3,893	1,862	190	158	85	0	0	0	6,188
Swindon	Rodbourne Cheney	8,678	Swindon North	2,575	2,872	215	179	99	0	0	0	5,940
Swindon	St Andrews	7,613	Swindon North	3,318	1,571	259	138	79	0	0	0	5,365
Swindon	St Margaret and South Marston	8,842	Swindon North	3,488	1,926	199	175	91	0	0	0	5,879
	Total	78,379		29,430	21,096	1,960	1,565	857	0	0	0	54,908

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

Old seat: Swindon South

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

Old seat: Swindon South				Transfer-adjusted Results
District	Ward	Electorate 2017	New Seat	CON Votes	LAB Votes	LIB Votes	UKIP Votes	Green Votes	NAT Votes	MIN Votes	OTH Votes	Total Votes
Swindon	Central	6,607	Swindon South	2,190	3,234	304	162	85	0	0	0	5,975
Swindon	Chiseldon and Lawn	4,663	Swindon South	1,886	811	84	64	38	0	0	0	2,883
Swindon	Covingham and Dorcan	1,647	Swindon North	609	424	36	31	14	0	0	0	1,114
Swindon	Eastcott	6,430	Swindon South	2,197	2,507	345	133	108	0	0	0	5,290
Swindon	Liden, Eldene and Park South	8,073	Swindon South	2,685	2,844	157	158	74	0	0	0	5,918
Swindon	Lydiard and Freshbrook	8,061	Swindon South	2,945	2,317	211	143	75	0	0	0	5,691
Swindon	Mannington and Western	2,876	Swindon South	994	1,080	54	59	34	0	0	0	2,221
Swindon	Old Town	7,248	Swindon South	2,488	1,609	203	100	78	0	0	0	4,478
Swindon	Ridgeway	2,484	Swindon South	1,088	467	72	36	9	0	0	0	1,672
Swindon	Shaw	7,799	Swindon South	3,070	2,066	210	134	79	0	0	0	5,559
Swindon	Walcot and Park North	8,250	Swindon South	2,321	3,624	191	168	93	0	0	0	6,397
Swindon	Wroughton and Wichelstowe	6,069	Swindon South	2,336	1,361	213	104	60	0	0	0	4,074
	Total	70,207		24,809	22,344	2,080	1,292	747	0	0	0	51,272

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

New seat: Swindon South

District	Ward	Electorate 2017	Old Seat	CON Votes	LAB Votes	LIB Votes	UKIP Votes	Green Votes	NAT Votes	MIN Votes	OTH Votes	Total Votes
New seat: Swindon South
Swindon	Central	8,436	Swindon South	2,190	3,234	304	162	85	0	0	0	5,975
Swindon	Chiseldon and Lawn	4,071	Swindon South	1,886	811	84	64	38	0	0	0	2,883
Swindon	Eastcott	7,470	Swindon South	2,197	2,507	345	133	108	0	0	0	5,290
Swindon	Liden, Eldene and Park South	8,357	Swindon South	2,685	2,844	157	158	74	0	0	0	5,918
Swindon	Lydiard and Freshbrook	8,035	Swindon South	2,945	2,317	211	143	75	0	0	0	5,691
Swindon	Mannington and Western	4,158	Swindon North	1,286	1,326	100	84	50	0	0	0	2,846
Swindon	Mannington and Western	3,135	Swindon South	994	1,080	54	59	34	0	0	0	2,221
Swindon	Old Town	6,323	Swindon South	2,488	1,609	203	100	78	0	0	0	4,478
Swindon	Ridgeway	2,361	Swindon South	1,088	467	72	36	9	0	0	0	1,672
Swindon	Shaw	7,847	Swindon South	3,070	2,066	210	134	79	0	0	0	5,559
Swindon	Walcot and Park North	9,032	Swindon South	2,321	3,624	191	168	93	0	0	0	6,397
Swindon	Wroughton and Wichelstowe	5,751	Swindon South	2,336	1,361	213	104	60	0	0	0	4,074
	Total	74,976		25,486	23,246	2,144	1,345	783	0	0	0	53,004

And these are the implied results for 2017 for the new seat of Swindon South. 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:	Robert Buckland (CON)
County/Area:	Wiltshire (South West)
Electorate:	74,976
Turnout:	70.7%

Swindon South: New Boundaries 2018 Calculation

Swindon South: Overview

Introduction