Trowbridge and West Wiltshire: New Boundaries 2018 Calculation

Trowbridge and West Wiltshire: Overview

Projection: CON seat

Implied MP at 2017:Michelle Donelan  (CON)
County/Area:Wiltshire (South West)
Electorate:81,812
Turnout:73.4%

PartyImplied 2017 VotesImplied 2017 Share
CON33,51455.8%
LAB13,72022.9%
LIB11,77019.6%
Green6841.1%
OTH2480.4%
UKIP840.1%
CON Majority19,79433.0%

See overview of other seats in South West.



Introduction

This page shows the detail of the calculations performed to estimate the general election result for 2017 had the new boundaries for Trowbridge and West 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.

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.

More details of the calculation formulas are available.

Trowbridge and West Wiltshire: Map

Boundary Lines courtesy of Ordnance Survey OpenData © Crown copyright 2015, Map © OpenStreetMap contributors

List of old seats forming part of Trowbridge and West Wiltshire

The old seat(s) needed are:

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: ChippenhamTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
WiltshireBradford-on-Avon North3,724Trowbridge and West Wiltshire1,357477958000002,792
WiltshireBradford-on-Avon South3,873Trowbridge and West Wiltshire1,308538957000002,803
WiltshireChippenham Cepen Park and Derriads3,326Chippenham and North Wiltshire1,668556402000002,626
WiltshireChippenham Cepen Park and Redlands3,301Chippenham and North Wiltshire1,791677428000002,896
WiltshireChippenham Hardenhuish3,210Chippenham and North Wiltshire1,436574831000002,841
WiltshireChippenham Hardens and England2,987Chippenham and North Wiltshire1,206582768000002,556
WiltshireChippenham Lowden and Rowden3,430Chippenham and North Wiltshire1,343595829000002,767
WiltshireChippenham Monkton2,921Chippenham and North Wiltshire1,029387800000002,216
WiltshireChippenham Pewsham3,266Chippenham and North Wiltshire1,283482948000002,713
WiltshireChippenham Queens and Sheldon3,244Chippenham and North Wiltshire1,305609768000002,682
WiltshireCorsham Pickwick3,378Trowbridge and West Wiltshire1,647842459000002,948
WiltshireCorsham Town3,712Trowbridge and West Wiltshire1,608438740000002,786
WiltshireCorsham Without and Box Hill2,311Trowbridge and West Wiltshire1,312324268000001,904
WiltshireHilperton3,737Trowbridge and West Wiltshire1,854570474000002,898
WiltshireHolt and Staverton3,334Trowbridge and West Wiltshire1,421385873000002,679
WiltshireMelksham Central3,675Trowbridge and West Wiltshire1,480721796000002,997
WiltshireMelksham North3,419Trowbridge and West Wiltshire1,402582763000002,747
WiltshireMelksham South3,963Trowbridge and West Wiltshire1,4155351,032000002,982
WiltshireMelksham Without North4,093Trowbridge and West Wiltshire1,778436405000002,619
WiltshireMelksham Without South3,915Trowbridge and West Wiltshire1,954554450000002,958
WiltshireSummerham and Seend784Trowbridge and West Wiltshire422667000000558
WiltshireWinsley and Westwood2,969Trowbridge and West Wiltshire1,246305617000002,168
 Total72,572 31,26511,23514,6360000057,136

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

Old seat: Devizes

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

Old seat: DevizesTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
WiltshireAldbourne and Ramsbury3,881Devizes and East Wiltshire1,905448197739000162,729
WiltshireBromham, Rowde and Potterne3,784Devizes and East Wiltshire1,575487183208810042,538
WiltshireBulford, Allington and Figheldean3,118Salisbury1,810421184747400172,580
WiltshireBurbage and the Bedwyns3,719Devizes and East Wiltshire1,74348616059750052,528
WiltshireDevizes and Roundway South3,392Devizes and East Wiltshire1,219608262738700192,268
WiltshireDevizes East3,003Devizes and East Wiltshire1,069720183707400142,130
WiltshireDevizes North3,028Devizes and East Wiltshire1,021747194698000202,131
WiltshireDurrington and Larkhill4,711Salisbury2,0986838391161090063,851
WiltshireLudgershall and Perham Down3,350Devizes and East Wiltshire2,081582209908800133,063
WiltshireMarlborough East3,170Devizes and East Wiltshire1,099505345678100152,112
WiltshireMarlborough West2,848Devizes and East Wiltshire1,435432218699400172,265
WiltshirePewsey3,743Devizes and East Wiltshire1,457641174637600102,421
WiltshirePewsey Vale3,451Devizes and East Wiltshire1,44640835357660032,333
WiltshireRoundway3,288Devizes and East Wiltshire1,504530192687900132,386
WiltshireSummerham and Seend1,152Trowbridge and West Wiltshire525121515723002779
WiltshireThe Collingbournes and Netheravon3,156Devizes and East Wiltshire1,57033613955640052,169
WiltshireThe Lavingtons and Erlestoke3,961Devizes and East Wiltshire1,92972521581970053,052
WiltshireTidworth3,759Devizes and East Wiltshire3,44373931313112900334,788
WiltshireUrchfont and The Cannings3,670Devizes and East Wiltshire1,312513153177710052,231
WiltshireWest Selkley3,224Devizes and East Wiltshire1,50347814151680032,244
 Total67,408 31,74410,6104,7051,7081,6060022550,598

The full details of these calculations are given on the Devizes 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 NorthTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
WiltshireBox and Colerne3,670Chippenham and North Wiltshire1,776503749286600453,167
WiltshireBrinkworth3,687Chippenham and North Wiltshire1,884392317445500212,713
WiltshireBy Brook3,475Chippenham and North Wiltshire1,960368306425200102,738
WiltshireCalne Central3,164Devizes and East Wiltshire1,156578659586300172,531
WiltshireCalne Chilvester and Abberd3,770Devizes and East Wiltshire1,623727575657600143,080
WiltshireCalne North3,095Devizes and East Wiltshire1,328647780606800232,906
WiltshireCalne Rural3,398Devizes and East Wiltshire1,831397273515400452,651
WiltshireCalne South and Cherhill3,689Devizes and East Wiltshire1,653491566566700262,859
WiltshireChippenham Cepen Park and Redlands54Chippenham and North Wiltshire271361100048
WiltshireChippenham Hardens and England18Chippenham and North Wiltshire7440000015
WiltshireCorsham Pickwick183Trowbridge and West Wiltshire82522334001165
WiltshireCorsham Without and Box Hill1,622Trowbridge and West Wiltshire86827816824310061,375
WiltshireCricklade and Latton3,816Chippenham and North Wiltshire1,654500762276600143,023
WiltshireKington3,822Chippenham and North Wiltshire2,081423363486100132,989
WiltshireLyneham2,876Chippenham and North Wiltshire2,273535380595700143,318
WiltshireMalmesbury3,790Chippenham and North Wiltshire1,592650877598000243,282
WiltshireMinety3,700Chippenham and North Wiltshire1,996437316515800202,878
WiltshirePurton3,637Chippenham and North Wiltshire1,848361272254200372,585
WiltshireRoyal Wootton Bassett East3,654Chippenham and North Wiltshire1,768416408255100112,679
WiltshireRoyal Wootton Bassett North3,395Chippenham and North Wiltshire1,410589563596300122,696
WiltshireRoyal Wootton Bassett South4,612Chippenham and North Wiltshire1,538604826667400143,122
WiltshireSherston3,891Chippenham and North Wiltshire2,043433328215000102,885
 Total67,018 32,3989,3989,5218721,1390037753,705

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

Old seat: Wiltshire South West

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

Old seat: Wiltshire South WestTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
WiltshireEthandune3,540Warminster and Shaftesbury1,54660230206700132,530
WiltshireFovant and Chalke Valley1,398Salisbury804168440200061,042
WiltshireMere3,319Warminster and Shaftesbury1,53061213806600592,405
WiltshireNadder and East Knoyle3,198Warminster and Shaftesbury1,67546110404900232,312
WiltshireSouthwick3,376Trowbridge and West Wiltshire1,60562716006400432,499
WiltshireSummerham and Seend1,480Trowbridge and West Wiltshire760188500210061,025
WiltshireTisbury3,370Warminster and Shaftesbury1,73351313505900112,451
WiltshireTrowbridge Adcroft3,128Trowbridge and West Wiltshire1,16681646407700152,538
WiltshireTrowbridge Central3,254Trowbridge and West Wiltshire1,3831,08055709700173,134
WiltshireTrowbridge Drynham2,967Trowbridge and West Wiltshire1,30561927906300112,277
WiltshireTrowbridge Grove3,188Trowbridge and West Wiltshire1,38476917907100512,454
WiltshireTrowbridge Lambrok3,504Trowbridge and West Wiltshire1,53088519307800462,732
WiltshireTrowbridge Park3,294Trowbridge and West Wiltshire1,32886533008400372,644
WiltshireTrowbridge Paxcroft3,715Trowbridge and West Wiltshire1,25460142106500122,353
WiltshireWarminster Broadway3,465Warminster and Shaftesbury1,70562217006300172,577
WiltshireWarminster Copheap and Wylye3,404Warminster and Shaftesbury2,14752713705300122,876
WiltshireWarminster East4,016Warminster and Shaftesbury1,79784621308400502,990
WiltshireWarminster West3,917Warminster and Shaftesbury1,99167218506600152,929
WiltshireWarminster Without3,327Warminster and Shaftesbury1,77439810204800102,332
WiltshireWestbury East3,576Warminster and Shaftesbury1,37778748608500532,788
WiltshireWestbury North3,228Warminster and Shaftesbury1,23276143807600372,544
WiltshireWestbury West3,627Warminster and Shaftesbury1,6951,05023908200483,114
WiltshireWinsley and Westwood292Trowbridge and West Wiltshire120463306001206
 Total71,583 32,84114,5155,35901,4440059354,752

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

New seat: Trowbridge and West Wiltshire

The new seat of Trowbridge and West Wiltshire is made up of the following wards, with the transfer-adjusted votes shown.

New seat: Trowbridge and West Wiltshire
DistrictWardElectorate
2017
Old Seat CON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
WiltshireBradford-on-Avon North3,735Chippenham1,357477958000002,792
WiltshireBradford-on-Avon South3,750Chippenham1,308538957000002,803
WiltshireCorsham Pickwick3,943Chippenham1,647842459000002,948
WiltshireCorsham Pickwick219Wiltshire North82522334001165
WiltshireCorsham Town3,727Chippenham1,608438740000002,786
WiltshireCorsham Without and Box Hill2,548Chippenham1,312324268000001,904
WiltshireCorsham Without and Box Hill1,828Wiltshire North86827816824310061,375
WiltshireHilperton3,877Chippenham1,854570474000002,898
WiltshireHolt and Staverton3,585Chippenham1,421385873000002,679
WiltshireMelksham Central4,010Chippenham1,480721796000002,997
WiltshireMelksham North3,675Chippenham1,402582763000002,747
WiltshireMelksham South3,989Chippenham1,4155351,032000002,982
WiltshireMelksham Without North3,505Chippenham1,778436405000002,619
WiltshireMelksham Without South3,956Chippenham1,954554450000002,958
WiltshireSouthwick3,508Wiltshire South West1,60562716006400432,499
WiltshireSummerham and Seend747Chippenham422667000000558
WiltshireSummerham and Seend1,111Devizes525121515723002779
WiltshireSummerham and Seend1,440Wiltshire South West760188500210061,025
WiltshireTrowbridge Adcroft3,564Wiltshire South West1,16681646407700152,538
WiltshireTrowbridge Central4,404Wiltshire South West1,3831,08055709700173,134
WiltshireTrowbridge Drynham3,199Wiltshire South West1,30561927906300112,277
WiltshireTrowbridge Grove3,445Wiltshire South West1,38476917907100512,454
WiltshireTrowbridge Lambrok3,838Wiltshire South West1,53088519307800462,732
WiltshireTrowbridge Park3,714Wiltshire South West1,32886533008400372,644
WiltshireTrowbridge Paxcroft3,304Wiltshire South West1,25460142106500122,353
WiltshireWinsley and Westwood2,899Chippenham1,246305617000002,168
WiltshireWinsley and Westwood292Wiltshire South West120463306001206
 Total81,812 33,51413,72011,770846840024860,020

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


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