Putney and Wandsworth Town: New Boundaries 2018 Calculation

Putney and Wandsworth Town: Overview

Projection: CON seat

Implied MP at 2017:Justine Greening  (CON)
County/Area:Wandsworth (London)
Electorate:75,620
Turnout:72.3%

PartyImplied 2017 VotesImplied 2017 Share
CON24,36844.5%
LAB22,49141.1%
LIB5,97510.9%
Green1,1852.2%
UKIP4690.9%
MIN1740.3%
OTH370.1%
CON Majority1,8773.4%

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 Putney and Wandsworth Town 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.

Putney and Wandsworth Town: Map

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

List of old seats forming part of Putney and Wandsworth Town

The old seat(s) needed are:

Old seat: Battersea

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

Old seat: BatterseaTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
WandsworthBalham10,443Tooting and Balham3,5013,06873042121016047,626
WandsworthFairfield9,986Putney and Wandsworth Town3,3103,14370647119017457,504
WandsworthLatchmere9,569Battersea and Clapham2,2144,83951469116020557,962
WandsworthNorthcote9,292Battersea and Clapham3,6722,87976740124015247,638
WandsworthQueenstown9,948Battersea and Clapham3,1134,37755870129017758,429
WandsworthShaftesbury9,921Battersea and Clapham3,2513,24455524116013847,332
WandsworthSt Mary's Park10,765Battersea and Clapham3,8163,74357165140022968,570
 Total69,924 22,87725,2934,40135786501,2353355,061

The full details of these calculations are given on the Battersea 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: Tooting

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

Old seat: TootingTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
WandsworthBedford10,234Tooting and Balham2,8434,545403401220007,953
WandsworthEarlsfield10,820Putney and Wandsworth Town3,0174,743476501120008,398
WandsworthFurzedown9,791Tooting and Balham1,9735,952314641370008,440
WandsworthGraveney9,892Tooting and Balham1,7505,838521441210008,274
WandsworthNightingale10,555Tooting and Balham3,3443,967472401190007,942
WandsworthTooting10,498Tooting and Balham2,3925,778494431300008,837
WandsworthWandsworth Common9,638Tooting and Balham3,9183,871377581030008,327
 Total71,428 19,23734,6943,05733984400058,171

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

New seat: Putney and Wandsworth Town

The new seat of Putney and Wandsworth Town is made up of the following wards, with the transfer-adjusted votes shown.

New seat: Putney and Wandsworth Town
DistrictWardElectorate
2017
Old Seat CON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
WandsworthEarlsfield11,255Tooting3,0174,743476501120008,398
WandsworthEast Putney10,470Putney3,6902,638965751790037,550
WandsworthFairfield10,571Battersea3,3103,14370647119017457,504
WandsworthSouthfields11,319Putney3,5033,3421,0464720700188,163
WandsworthThamesfield10,327Putney3,7282,4291,020672020037,449
WandsworthWest Hill11,411Putney3,4623,579913921800038,229
WandsworthWest Putney10,267Putney3,6582,617849911860057,406
 Total75,620 24,36822,4915,9754691,18501743754,699

And these are the implied results for 2017 for the new seat of Putney and Wandsworth Town. 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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