New Seat Details - Chippenham and North Wiltshire

This page shows the detail of the calculations performed to estimate the general election result for 2017 had the new boundaries for Chippenham and North Wiltshire 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	34,918	58.7%
LIB	12,251	20.6%
LAB	10,690	18.0%
Green	776	1.3%
UKIP	555	0.9%
OTH	245	0.4%
CON Majority	22,667	38.1%

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.

Chippenham and North Wiltshire: Map

List of old seats forming part of Chippenham and North Wiltshire

Old seat: Chippenham

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

Old seat: Chippenham				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
Wiltshire	Bradford-on-Avon North	3,724	Trowbridge and West Wiltshire	1,357	477	958	0	0	0	0	0	2,792
Wiltshire	Bradford-on-Avon South	3,873	Trowbridge and West Wiltshire	1,308	538	957	0	0	0	0	0	2,803
Wiltshire	Chippenham Cepen Park and Derriads	3,326	Chippenham and North Wiltshire	1,668	556	402	0	0	0	0	0	2,626
Wiltshire	Chippenham Cepen Park and Redlands	3,301	Chippenham and North Wiltshire	1,791	677	428	0	0	0	0	0	2,896
Wiltshire	Chippenham Hardenhuish	3,210	Chippenham and North Wiltshire	1,436	574	831	0	0	0	0	0	2,841
Wiltshire	Chippenham Hardens and England	2,987	Chippenham and North Wiltshire	1,206	582	768	0	0	0	0	0	2,556
Wiltshire	Chippenham Lowden and Rowden	3,430	Chippenham and North Wiltshire	1,343	595	829	0	0	0	0	0	2,767
Wiltshire	Chippenham Monkton	2,921	Chippenham and North Wiltshire	1,029	387	800	0	0	0	0	0	2,216
Wiltshire	Chippenham Pewsham	3,266	Chippenham and North Wiltshire	1,283	482	948	0	0	0	0	0	2,713
Wiltshire	Chippenham Queens and Sheldon	3,244	Chippenham and North Wiltshire	1,305	609	768	0	0	0	0	0	2,682
Wiltshire	Corsham Pickwick	3,378	Trowbridge and West Wiltshire	1,647	842	459	0	0	0	0	0	2,948
Wiltshire	Corsham Town	3,712	Trowbridge and West Wiltshire	1,608	438	740	0	0	0	0	0	2,786
Wiltshire	Corsham Without and Box Hill	2,311	Trowbridge and West Wiltshire	1,312	324	268	0	0	0	0	0	1,904
Wiltshire	Hilperton	3,737	Trowbridge and West Wiltshire	1,854	570	474	0	0	0	0	0	2,898
Wiltshire	Holt and Staverton	3,334	Trowbridge and West Wiltshire	1,421	385	873	0	0	0	0	0	2,679
Wiltshire	Melksham Central	3,675	Trowbridge and West Wiltshire	1,480	721	796	0	0	0	0	0	2,997
Wiltshire	Melksham North	3,419	Trowbridge and West Wiltshire	1,402	582	763	0	0	0	0	0	2,747
Wiltshire	Melksham South	3,963	Trowbridge and West Wiltshire	1,415	535	1,032	0	0	0	0	0	2,982
Wiltshire	Melksham Without North	4,093	Trowbridge and West Wiltshire	1,778	436	405	0	0	0	0	0	2,619
Wiltshire	Melksham Without South	3,915	Trowbridge and West Wiltshire	1,954	554	450	0	0	0	0	0	2,958
Wiltshire	Summerham and Seend	784	Trowbridge and West Wiltshire	422	66	70	0	0	0	0	0	558
Wiltshire	Winsley and Westwood	2,969	Trowbridge and West Wiltshire	1,246	305	617	0	0	0	0	0	2,168
	Total	72,572		31,265	11,235	14,636	0	0	0	0	0	57,136

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

Old seat: Wiltshire North

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

Old seat: Wiltshire 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
Wiltshire	Box and Colerne	3,670	Chippenham and North Wiltshire	1,776	503	749	28	66	0	0	45	3,167
Wiltshire	Brinkworth	3,687	Chippenham and North Wiltshire	1,884	392	317	44	55	0	0	21	2,713
Wiltshire	By Brook	3,475	Chippenham and North Wiltshire	1,960	368	306	42	52	0	0	10	2,738
Wiltshire	Calne Central	3,164	Devizes and East Wiltshire	1,156	578	659	58	63	0	0	17	2,531
Wiltshire	Calne Chilvester and Abberd	3,770	Devizes and East Wiltshire	1,623	727	575	65	76	0	0	14	3,080
Wiltshire	Calne North	3,095	Devizes and East Wiltshire	1,328	647	780	60	68	0	0	23	2,906
Wiltshire	Calne Rural	3,398	Devizes and East Wiltshire	1,831	397	273	51	54	0	0	45	2,651
Wiltshire	Calne South and Cherhill	3,689	Devizes and East Wiltshire	1,653	491	566	56	67	0	0	26	2,859
Wiltshire	Chippenham Cepen Park and Redlands	54	Chippenham and North Wiltshire	27	13	6	1	1	0	0	0	48
Wiltshire	Chippenham Hardens and England	18	Chippenham and North Wiltshire	7	4	4	0	0	0	0	0	15
Wiltshire	Corsham Pickwick	183	Trowbridge and West Wiltshire	82	52	23	3	4	0	0	1	165
Wiltshire	Corsham Without and Box Hill	1,622	Trowbridge and West Wiltshire	868	278	168	24	31	0	0	6	1,375
Wiltshire	Cricklade and Latton	3,816	Chippenham and North Wiltshire	1,654	500	762	27	66	0	0	14	3,023
Wiltshire	Kington	3,822	Chippenham and North Wiltshire	2,081	423	363	48	61	0	0	13	2,989
Wiltshire	Lyneham	2,876	Chippenham and North Wiltshire	2,273	535	380	59	57	0	0	14	3,318
Wiltshire	Malmesbury	3,790	Chippenham and North Wiltshire	1,592	650	877	59	80	0	0	24	3,282
Wiltshire	Minety	3,700	Chippenham and North Wiltshire	1,996	437	316	51	58	0	0	20	2,878
Wiltshire	Purton	3,637	Chippenham and North Wiltshire	1,848	361	272	25	42	0	0	37	2,585
Wiltshire	Royal Wootton Bassett East	3,654	Chippenham and North Wiltshire	1,768	416	408	25	51	0	0	11	2,679
Wiltshire	Royal Wootton Bassett North	3,395	Chippenham and North Wiltshire	1,410	589	563	59	63	0	0	12	2,696
Wiltshire	Royal Wootton Bassett South	4,612	Chippenham and North Wiltshire	1,538	604	826	66	74	0	0	14	3,122
Wiltshire	Sherston	3,891	Chippenham and North Wiltshire	2,043	433	328	21	50	0	0	10	2,885
	Total	67,018		32,398	9,398	9,521	872	1,139	0	0	377	53,705

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

New seat: Chippenham and North Wiltshire

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: Chippenham and North Wiltshire
Wiltshire	Box and Colerne	4,211	Wiltshire North	1,776	503	749	28	66	0	0	45	3,167
Wiltshire	Brinkworth	3,608	Wiltshire North	1,884	392	317	44	55	0	0	21	2,713
Wiltshire	By Brook	3,642	Wiltshire North	1,960	368	306	42	52	0	0	10	2,738
Wiltshire	Chippenham Cepen Park and Derriads	3,513	Chippenham	1,668	556	402	0	0	0	0	0	2,626
Wiltshire	Chippenham Cepen Park and Redlands	3,875	Chippenham	1,791	677	428	0	0	0	0	0	2,896
Wiltshire	Chippenham Cepen Park and Redlands	64	Wiltshire North	27	13	6	1	1	0	0	0	48
Wiltshire	Chippenham Hardenhuish	3,801	Chippenham	1,436	574	831	0	0	0	0	0	2,841
Wiltshire	Chippenham Hardens and England	3,419	Chippenham	1,206	582	768	0	0	0	0	0	2,556
Wiltshire	Chippenham Hardens and England	21	Wiltshire North	7	4	4	0	0	0	0	0	15
Wiltshire	Chippenham Lowden and Rowden	3,702	Chippenham	1,343	595	829	0	0	0	0	0	2,767
Wiltshire	Chippenham Monkton	2,964	Chippenham	1,029	387	800	0	0	0	0	0	2,216
Wiltshire	Chippenham Pewsham	3,628	Chippenham	1,283	482	948	0	0	0	0	0	2,713
Wiltshire	Chippenham Queens and Sheldon	3,587	Chippenham	1,305	609	768	0	0	0	0	0	2,682
Wiltshire	Cricklade and Latton	4,020	Wiltshire North	1,654	500	762	27	66	0	0	14	3,023
Wiltshire	Kington	3,975	Wiltshire North	2,081	423	363	48	61	0	0	13	2,989
Wiltshire	Lyneham	4,412	Wiltshire North	2,273	535	380	59	57	0	0	14	3,318
Wiltshire	Malmesbury	4,364	Wiltshire North	1,592	650	877	59	80	0	0	24	3,282
Wiltshire	Minety	3,827	Wiltshire North	1,996	437	316	51	58	0	0	20	2,878
Wiltshire	Purton	3,437	Wiltshire North	1,848	361	272	25	42	0	0	37	2,585
Wiltshire	Royal Wootton Bassett East	3,562	Wiltshire North	1,768	416	408	25	51	0	0	11	2,679
Wiltshire	Royal Wootton Bassett North	3,583	Wiltshire North	1,410	589	563	59	63	0	0	12	2,696
Wiltshire	Royal Wootton Bassett South	4,152	Wiltshire North	1,538	604	826	66	74	0	0	14	3,122
Wiltshire	Sherston	3,836	Wiltshire North	2,043	433	328	21	50	0	0	10	2,885
	Total	79,203		34,918	10,690	12,251	555	776	0	0	245	59,435

And these are the implied results for 2017 for the new seat of Chippenham and North Wiltshire. 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:	James Gray (CON)
County/Area:	Wiltshire (South West)
Electorate:	79,203
Turnout:	75.0%

Chippenham and North Wiltshire: New Boundaries 2018 Calculation

Chippenham and North Wiltshire: Overview

Introduction