Prestwich and Middleton: New Boundaries 2018 Calculation

Prestwich and Middleton: Overview

 Projection: LAB seat 

Implied MP at 2017: Ivan Lewis  (LAB)
County/Area: Western Manchester (North West)
Electorate: 76,824
Turnout: 70.1%

 Implied 2017 VotesImplied 2017 Share
LAB29,99555.7%
CON20,07137.3%
UKIP2,3484.4%
LIB1,3172.4%
OTH900.2%
LAB Majority9,92418.4%

See overview of other seats in North West.

Prestwich and Middleton : Political and Demographic indicators

The table below shows some political and demographic numerical indicators for the new Prestwich and Middleton constituency, the 'North West' area and nation.

The political measures include the Left/Right and International/National axes (what does this mean).

The demographic measures are from the 2011 Census and include categories relating to national identity, economic activity, health and education. These categories are those which have the most relevance to political attitudes.

IndicatorSeatNorth WestAll GB
Party WinnerLABLABCON
Economic Position6° Left6° Left
National Position7° Nat2° Nat1° Int
EU Leave %57%54%52%
British Identity25%28%29%
Good Health46%46%48%
UK Born92%92%88%
Good Education34%37%39%
Good Job50%49%51%
High SEC49%48%51%
Average Age48.648.648.5
ABC1 Class49%50%53%

Prestwich and Middleton ranks #196 for "Leave", #441 for "Right" and #201 for "National" out of 600 new seats.

Indicators: Legend and Descriptions

Indicators : Legend and Descriptions

The colour scheme used in the table above is explained in the legend table below. The eight census indicators (British Identity, Good Health, UK Born, Good Education, Good Job, High SEC, Average Age and AB1 Class) all use the same 'Census' colour scheme indicating whether the area's level is above or below the national average.

TopicCat 1Cat 2Cat 3Cat 4Cat 5
Economic PositionVery LeftLeftCentristRightVery Right
National PositionVery IntInternationalCentristNationalVery Nat
EU Leave %Very RemainRemainBalancedLeaveVery Leave
CensusVery LowLowMediumHighVery High

Indicator definitions are given in terms of political data definitions or census categories:

IndicatorCensus
Question
Definition / Included Census Categories
Party WinnerArea party winner : actual election result or projected by Electoral Calculus
Economic PositionEconomic position between 100° Left and 100° Right, estimated by Electoral Calculus from political and demographic data.
National PositionNational position between 100° International and 100° National, estimated by Electoral Calculus from political and demographic data.
EU Leave %EU Referendum vote share for 'Leave' : actual result or estimate
British IdentityNational Identity (KS202)Those answering British, British-Other, or Scottish-British
Good HealthHealth (KS301)Those answering 'Very Good Health'
UK BornCountry of Birth (QS203)Those answering England, Northern Ireland, Scotland, Wales, GB Other, or UK Other
Good EducationHighest level of Qualification (QS501)Level 3 (A-level equivalent) or Level 4+ (degree equivalent)
Good JobOccupation (QS606)Occupation codes 1xx to 4xx (Managers, Professionals, Associates, and office workers)
High SECNS-SeC of Household Reference Person (QS609)National Statistics Socio-economic Classification from 1 to 4 (higher managers and professionals, lower managers and professionals, intermediate occupations, small employers and self-employed).
Average AgeAge (QS103)Average age of adults (18 years and above)
ABC1 ClassApproximated Social Grade (QS611)Approximated social grades A, B and C1

Prestwich and Middleton: Map

Boundary Lines courtesy of Ordnance Survey OpenData © Crown copyright 2015

Introduction

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

List of old seats forming part of Prestwich and Middleton

The old seat(s) needed are:

Old seat: Bury South

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

Old seat: Bury SouthTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
BuryBesses8,270Prestwich and Middleton1,9363,379192177000375,721
BuryHolyrood8,450Prestwich and Middleton2,1953,23431784000135,843
BuryPilkington Park7,251Farnworth2,9242,007195600085,014
BuryRadcliffe East8,661Bury2,2943,267362780001165,991
BuryRadcliffe North8,212Farnworth2,3113,04873233000145,679
BuryRadcliffe West8,482Farnworth2,1803,40826237000155,866
BurySedgley9,788Prestwich and Middleton3,1033,45314756000116,770
BurySt Mary's7,690Prestwich and Middleton2,0632,97917882000185,320
BuryUnsworth6,919Prestwich and Middleton2,1942,38978113000114,785
 Total73,723 21,20027,1641,0661,31600024350,989

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

Old seat: Heywood and Middleton

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

Old seat: Heywood and MiddletonTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
RochdaleBamford7,532Rochdale2,5341,88213914600004,701
RochdaleCastleton7,804Rochdale1,7592,71313726200004,871
RochdaleEast Middleton7,942Prestwich and Middleton1,6922,8357735300004,957
RochdaleHopwood Hall8,379Prestwich and Middleton1,9662,8125639400005,228
RochdaleNorden7,541Rochdale2,8291,58013616100004,706
RochdaleNorth Heywood7,742Rochdale1,5942,65119739000004,832
RochdaleNorth Middleton7,973Prestwich and Middleton1,5472,95511136300004,976
RochdaleSouth Middleton7,402Prestwich and Middleton1,9292,26312929800004,619
RochdaleWest Heywood8,608Rochdale1,6653,1907144500005,371
RochdaleWest Middleton8,978Prestwich and Middleton1,4463,6963242800005,602
 Total79,901 18,96126,5771,0853,240000049,863

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

New seat: Prestwich and Middleton

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

New seat: Prestwich and Middleton
DistrictWardElectorate
2017
Old Seat CON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
NAT
Votes
MIN
Votes
OTH
Votes
Total
Votes
BuryBesses7,667Bury South1,9363,379192177000375,721
BuryHolyrood8,333Bury South2,1953,23431784000135,843
BurySedgley8,128Bury South3,1033,45314756000116,770
BurySt Mary's7,371Bury South2,0632,97917882000185,320
BuryUnsworth7,030Bury South2,1942,38978113000114,785
RochdaleEast Middleton7,371Heywood and Middleton1,6922,8357735300004,957
RochdaleHopwood Hall7,798Heywood and Middleton1,9662,8125639400005,228
RochdaleNorth Middleton7,462Heywood and Middleton1,5472,95511136300004,976
RochdaleSouth Middleton7,631Heywood and Middleton1,9292,26312929800004,619
RochdaleWest Middleton8,033Heywood and Middleton1,4463,6963242800005,602
 Total76,824 20,07129,9951,3172,3480009053,821

And these are the implied results for 2017 for the new seat of Prestwich and Middleton.


© 2017 Martin Baxter
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