Spelthorne: New Boundaries 2018 Calculation

Spelthorne: Overview

Projection: CON seat

Implied MP at 2017:Kwasi Kwarteng  (CON)
County/Area:Surrey (South East)
Electorate:76,648
Turnout:69.0%

PartyImplied 2017 VotesImplied 2017 Share
CON30,37157.4%
LAB15,96530.2%
LIB2,9535.6%
UKIP2,4274.6%
Green1,1592.2%
CON Majority14,40627.2%

See overview of other seats in South East.



Introduction

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

Spelthorne: Map

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

List of old seats forming part of Spelthorne

The old seat(s) needed are:

Old seat: Runnymede and Weybridge

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

Old seat: Runnymede and WeybridgeTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
ElmbridgeOatlands Park4,694Runnymede and Weybridge2,140539298901340003,201
ElmbridgeSt George's Hill4,196Runnymede and Weybridge2,38460515651590003,255
ElmbridgeWeybridge North3,089Runnymede and Weybridge1,28149833638450002,198
ElmbridgeWeybridge South3,188Runnymede and Weybridge1,41044235475480002,329
RunnymedeAddlestone Bourneside4,005Runnymede and Weybridge1,5078121931031550002,770
RunnymedeAddlestone North4,226Runnymede and Weybridge1,675967184106520002,984
RunnymedeChertsey Meads4,227Runnymede and Weybridge1,794888190109550003,036
RunnymedeChertsey South and Row Town4,638Runnymede and Weybridge1,66271316098440002,677
RunnymedeChertsey St Ann's4,259Runnymede and Weybridge1,730968198113570003,066
RunnymedeEgham Hythe4,510Runnymede and Weybridge1,7341,140215116570003,262
RunnymedeEgham Town3,912Runnymede and Weybridge1,7961,04724462790003,228
RunnymedeEnglefield Green East2,146Runnymede and Weybridge1,617715163901560002,741
RunnymedeEnglefield Green West3,142Runnymede and Weybridge1,432770157891540002,602
RunnymedeFoxhills3,995Runnymede and Weybridge1,817733165103520002,870
RunnymedeNew Haw4,211Runnymede and Weybridge1,850704260112530002,979
RunnymedeThorpe4,119Spelthorne1,678698199131540002,760
RunnymedeVirginia Water3,936Runnymede and Weybridge2,19252513396460002,992
RunnymedeWoodham4,146Runnymede and Weybridge1,74062316094470002,664
 Total70,639 31,43913,3873,7651,6761,34700051,614

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

Old seat: Spelthorne

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

Old seat: SpelthorneTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
SpelthorneAshford Common6,049Spelthorne2,5951,231139215530004,233
SpelthorneAshford East5,619Spelthorne2,3431,074122192480003,779
SpelthorneAshford North and Stanwell South5,814Spelthorne2,1521,6451572061180004,278
SpelthorneAshford Town5,265Spelthorne2,1731,0691461811430003,712
SpelthorneHalliford and Sunbury West4,679Spelthorne1,868849307148500003,222
SpelthorneLaleham and Shepperton Green5,900Spelthorne2,5311,156215206590004,167
SpelthorneRiverside and Laleham5,170Spelthorne2,2418381901301270003,526
SpelthorneShepperton Town5,243Spelthorne2,316818166157530003,510
SpelthorneStaines5,430Spelthorne2,3101,2951911571710004,124
SpelthorneStaines South5,145Spelthorne1,9091,367244180500003,750
SpelthorneStanwell North5,356Spelthorne1,8971,7041281921160004,037
SpelthorneSunbury Common5,470Spelthorne2,1691,384417204630004,237
SpelthorneSunbury East5,159Spelthorne2,189837332128540003,540
 Total70,299 28,69315,2672,7542,2961,10500050,115

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

New seat: Spelthorne

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

New seat: Spelthorne
DistrictWardElectorate
2017
Old Seat CON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
RunnymedeThorpe4,006Runnymede and Weybridge1,678698199131540002,760
SpelthorneAshford Common6,136Spelthorne2,5951,231139215530004,233
SpelthorneAshford East5,478Spelthorne2,3431,074122192480003,779
SpelthorneAshford North and Stanwell South6,202Spelthorne2,1521,6451572061180004,278
SpelthorneAshford Town5,378Spelthorne2,1731,0691461811430003,712
SpelthorneHalliford and Sunbury West4,672Spelthorne1,868849307148500003,222
SpelthorneLaleham and Shepperton Green6,040Spelthorne2,5311,156215206590004,167
SpelthorneRiverside and Laleham5,110Spelthorne2,2418381901301270003,526
SpelthorneShepperton Town5,087Spelthorne2,316818166157530003,510
SpelthorneStaines5,977Spelthorne2,3101,2951911571710004,124
SpelthorneStaines South5,436Spelthorne1,9091,367244180500003,750
SpelthorneStanwell North5,852Spelthorne1,8971,7041281921160004,037
SpelthorneSunbury Common6,142Spelthorne2,1691,384417204630004,237
SpelthorneSunbury East5,132Spelthorne2,189837332128540003,540
 Total76,648 30,37115,9652,9532,4271,15900052,875

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