Cambridge: New Boundaries 2018 Calculation

Cambridge: Overview

Projection: LAB seat

Implied MP at 2017:Daniel Zeichner  (LAB)
County/Area:Cambridgeshire (Anglia)
Electorate:85,072
Turnout:72.1%

PartyImplied 2017 VotesImplied 2017 Share
LAB30,94550.5%
LIB17,80429.0%
CON10,99917.9%
Green1,4352.3%
OTH1350.2%
LAB Majority13,14121.4%

See overview of other seats in Anglia.



Introduction

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

Cambridge: Map

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

List of old seats forming part of Cambridge

The old seat(s) needed are:

Old seat: Cambridge

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

Old seat: CambridgeTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
CambridgeAbbey5,522Cambridge7262,7711,21009800124,817
CambridgeArbury5,338Cambridge5932,4621,312010300114,481
CambridgeCastle5,086Cambridge9912,1621,500010300174,773
CambridgeCherry Hinton5,449Cambridge8062,4191,0320830064,346
CambridgeColeridge5,280Cambridge7882,4121,27401030064,583
CambridgeEast Chesterton5,459Cambridge6962,4351,32309700114,562
CambridgeKing's Hedges5,075Cambridge6212,5691,11808900354,432
CambridgeMarket4,528Cambridge5991,6941,09608500123,486
CambridgeNewnham4,596Cambridge7371,7331,2860830043,843
CambridgePetersfield4,275Cambridge4822,3271,12701140054,055
CambridgeRomsey5,210Cambridge5222,4001,45301160064,497
CambridgeTrumpington6,347Cambridge9741,6751,1810850053,920
CambridgeWest Chesterton5,101Cambridge5981,9731,45801060054,140
 Total67,266 9,13329,03216,37001,2650013555,935

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

Old seat: Cambridgeshire South

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

Old seat: Cambridgeshire SouthTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
CambridgeQueen Edith's5,491Cambridge1,8661,9131,43401700005,383
South CambridgeshireBar Hill3,638Cambridgeshire South1,5478914560920002,986
South CambridgeshireBarton1,887Cambridgeshire South9073431900440001,484
South CambridgeshireBassingbourn3,364Letchworth and Royston1,7828013380820003,003
South CambridgeshireBourn7,462Cambridgeshire South3,2322,00971901450006,105
South CambridgeshireCaldecote1,829Cambridgeshire South6543074620210001,444
South CambridgeshireComberton1,761Cambridgeshire South8043392130400001,396
South CambridgeshireCottenham5,954Cambridgeshire South2,4791,33281501410004,767
South CambridgeshireDuxford2,089Cambridgeshire South9644122420390001,657
South CambridgeshireFowlmere and Foxton1,870Cambridgeshire South8613431830460001,433
South CambridgeshireGamlingay3,850Cambridgeshire South1,3716468580360002,911
South CambridgeshireGirton3,232Cambridgeshire South1,3857834410850002,694
South CambridgeshireHardwick1,995Cambridgeshire South7994213270410001,588
South CambridgeshireHarston and Hauxton1,863Cambridgeshire South6873034170200001,427
South CambridgeshireHaslingfield and The Eversdens2,141Cambridgeshire South7203274990230001,569
South CambridgeshireLongstanton2,336Cambridgeshire South1,0183471900190001,574
South CambridgeshireMelbourn4,170Letchworth and Royston1,4557681,0610410003,325
South CambridgeshireMeldreth2,056Letchworth and Royston6433744670180001,502
South CambridgeshireOrwell and Barrington1,892Cambridgeshire South6773093610320001,379
South CambridgeshirePapworth and Elsworth4,091Cambridgeshire South1,6607733900710002,894
South CambridgeshireSawston5,272Cambridgeshire South2,2801,33751601080004,241
South CambridgeshireSwavesey1,827Cambridgeshire South8893472010200001,457
South CambridgeshireThe Abingtons1,764Cambridgeshire South8703101550180001,353
South CambridgeshireThe Mordens1,888Letchworth and Royston8553681860170001,426
South CambridgeshireThe Shelfords and Stapleford5,577Cambridgeshire South2,2501,22272701270004,326
South CambridgeshireWhittlesford2,069Cambridgeshire South9753552510180001,599
 Total81,368 33,63017,68012,09901,51400064,923

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

New seat: Cambridge

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

New seat: Cambridge
DistrictWardElectorate
2017
Old Seat CON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
CambridgeAbbey6,718Cambridge7262,7711,21009800124,817
CambridgeArbury6,248Cambridge5932,4621,312010300114,481
CambridgeCastle6,655Cambridge9912,1621,500010300174,773
CambridgeCherry Hinton6,062Cambridge8062,4191,0320830064,346
CambridgeColeridge6,392Cambridge7882,4121,27401030064,583
CambridgeEast Chesterton6,362Cambridge6962,4351,32309700114,562
CambridgeKing's Hedges6,181Cambridge6212,5691,11808900354,432
CambridgeMarket4,862Cambridge5991,6941,09608500123,486
CambridgeNewnham5,361Cambridge7371,7331,2860830043,843
CambridgePetersfield5,653Cambridge4822,3271,12701140054,055
CambridgeQueen Edith's7,069Cambridgeshire South1,8661,9131,43401700005,383
CambridgeRomsey6,272Cambridge5222,4001,45301160064,497
CambridgeTrumpington5,465Cambridge9741,6751,1810850053,920
CambridgeWest Chesterton5,772Cambridge5981,9731,45801060054,140
 Total85,072 10,99930,94517,80401,4350013561,318

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