Wimbledon: New Boundaries 2018 Calculation

Wimbledon: Overview

Projection: CON seat

Implied MP at 2017:Stephen Hammond  (CON)
County/Area:Merton (London)
Electorate:85,124
Turnout:75.9%

PartyImplied 2017 VotesImplied 2017 Share
CON27,89643.2%
LAB25,97940.2%
LIB8,42413.0%
Green1,5422.4%
UKIP7091.1%
OTH630.1%
CON Majority1,9173.0%

See overview of other seats in London.



Introduction

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

Wimbledon: Map

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

List of old seats forming part of Wimbledon

The old seat(s) needed are:

Old seat: Mitcham and Morden

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

Old seat: Mitcham and MordenTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
MertonColliers Wood6,511Wimbledon1,3113,1362965215700374,989
MertonCricket Green7,142Mitcham and Norbury1,1163,886117695100415,280
MertonFigge's Marsh6,997Mitcham and Norbury1,0413,992121754500105,284
MertonGraveney5,860Mitcham and Norbury9703,263181574800484,567
MertonLavender Fields6,198Mitcham and Norbury1,0083,438156142490094,802
MertonLongthornton6,583Mitcham and Norbury1,1913,24812374430094,688
MertonLower Morden6,491Sutton and Cheam1,6412,2681241363600204,225
MertonPollards Hill7,185Mitcham and Norbury1,0453,4081011594300214,777
MertonRavensbury6,411Mitcham and Norbury1,1093,11513214512700144,642
MertonSt Helier6,942Sutton and Cheam1,2333,2841441454500144,865
 Total66,320 11,66533,0381,4951,0546440022348,119

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

Old seat: Putney

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

Old seat: PutneyTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
WandsworthEast Putney10,060Putney and Wandsworth Town3,6902,638965751790037,550
WandsworthRoehampton and Putney Heath8,269Wimbledon2,6384,52065610615400268,100
WandsworthSouthfields11,168Putney and Wandsworth Town3,5033,3421,0464720700188,163
WandsworthThamesfield10,761Putney and Wandsworth Town3,7282,4291,020672020037,449
WandsworthWest Hill9,704Putney and Wandsworth Town3,4623,579913921800038,229
WandsworthWest Putney9,860Putney and Wandsworth Town3,6582,617849911860057,406
 Total59,822 20,67919,1255,4494781,108005846,897

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

Old seat: Wimbledon

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

Old seat: WimbledonTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
MertonAbbey6,376Wimbledon1,9832,698605551690005,510
MertonCannon Hill6,559Wimbledon2,0552,25547374630004,920
MertonDundonald6,046Wimbledon2,1611,6301,05250820004,975
MertonHillside5,666Wimbledon2,4811,48471345770004,800
MertonMerton Park6,329Wimbledon2,3971,88066335980005,073
MertonRaynes Park6,607Wimbledon2,5921,68379961770005,212
MertonTrinity6,424Wimbledon2,2042,042725552060005,232
MertonVillage5,633Wimbledon3,11591138137940004,538
MertonWest Barnes6,831Wimbledon2,1991,5891,260751500005,273
MertonWimbledon Park7,034Wimbledon2,7602,151801642150005,991
 Total63,505 23,94718,3237,4725511,23100051,524

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

New seat: Wimbledon

The new seat of Wimbledon is made up of the following wards, with the transfer-adjusted votes shown.

New seat: Wimbledon
DistrictWardElectorate
2017
Old Seat CON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
MertonAbbey7,140Wimbledon1,9832,698605551690005,510
MertonCannon Hill6,376Wimbledon2,0552,25547374630004,920
MertonColliers Wood7,120Mitcham and Morden1,3113,1362965215700374,989
MertonDundonald6,448Wimbledon2,1611,6301,05250820004,975
MertonHillside6,219Wimbledon2,4811,48471345770004,800
MertonMerton Park6,574Wimbledon2,3971,88066335980005,073
MertonRaynes Park6,755Wimbledon2,5921,68379961770005,212
MertonTrinity6,782Wimbledon2,2042,042725552060005,232
MertonVillage5,881Wimbledon3,11591138137940004,538
MertonWest Barnes6,833Wimbledon2,1991,5891,260751500005,273
MertonWimbledon Park7,764Wimbledon2,7602,151801642150005,991
WandsworthRoehampton and Putney Heath11,232Putney2,6384,52065610615400268,100
 Total85,124 27,89625,9798,4247091,542006364,613

And these are the implied results for 2017 for the new seat of Wimbledon. 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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