Merthyr Tydfil and Rhymney: New Boundaries 2018 Calculation

Merthyr Tydfil and Rhymney: Overview

 Projection: LAB seat 

Implied MP at 2017: Gerald Jones  (LAB)
County/Area: Mid Glamorgan (Wales)
Electorate: 77,771
Turnout: 64.5%

 Implied 2017 VotesImplied 2017 Share
LAB33,11166.0%
CON9,09018.1%
Plaid4,8019.6%
UKIP1,9233.8%
LIB1,1192.2%
Green1180.2%
LAB Majority24,02147.9%

See overview of other seats in Wales.

Merthyr Tydfil and Rhymney : Political and Demographic indicators

The table below shows some political and demographic numerical indicators for the new Merthyr Tydfil and Rhymney constituency, the 'Wales' 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.

IndicatorSeatWalesAll GB
Party WinnerLABLABCON
Economic Position20° Left10° Left
National Position2° Int3° Int1° Int
EU Leave %57%53%52%
British Identity21%26%29%
Good Health41%47%48%
UK Born94%95%88%
Good Education28%36%39%
Good Job41%46%51%
High SEC40%46%51%
Average Age49.149.648.5
ABC1 Class40%47%53%

Merthyr Tydfil and Rhymney ranks #218 for "Leave", #580 for "Right" and #413 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

Merthyr Tydfil and Rhymney: 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 Merthyr Tydfil and Rhymney 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 Merthyr Tydfil and Rhymney

The old seat(s) needed are:

Old seat: Caerphilly

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

Old seat: CaerphillyTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
Plaid
Votes
MIN
Votes
OTH
Votes
Total
Votes
CaerphillyAber Valley5,033Caerphilly6411,7363310952657003,228
CaerphillyBargoed4,621Merthyr Tydfil and Rhymney4072,044246513411002,964
CaerphillyBedwas, Trethomas and Machen7,966Caerphilly1,2583,1076415438488005,109
CaerphillyGilfach1,494Merthyr Tydfil and Rhymney127686243697800960
CaerphillyHengoed4,101Merthyr Tydfil and Rhymney5571,4722210829443002,631
CaerphillyLlanbradach3,290Caerphilly609930549543380002,111
CaerphillyMorgan Jones5,051Caerphilly9891,5125811527539003,240
CaerphillyNelson3,443Merthyr Tydfil and Rhymney5901,251897532172002,209
CaerphillyPenyrheol9,232Caerphilly1,6183,0257818771943005,922
CaerphillySt Cattwg5,792Merthyr Tydfil and Rhymney5462,64346788393003,714
CaerphillySt James4,404Caerphilly8541,444245639406002,823
CaerphillySt Martins6,211Caerphilly1,5171,51216212657610003,984
CaerphillyYstrad Mynach3,743Merthyr Tydfil and Rhymney6991,131475627441002,401
 Total64,381 10,41222,4937251,2604455,9610041,296

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

Old seat: Islwyn

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

Old seat: IslwynTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
Plaid
Votes
MIN
Votes
OTH
Votes
Total
Votes
CaerphillyAberbargoed2,712Merthyr Tydfil and Rhymney921,47628200124001,740
CaerphillyAbercarn3,991Caerphilly5631,72041640172002,560
CaerphillyArgoed2,063Blaenau Gwent29480240720117001,325
CaerphillyBlackwood6,327Blaenau Gwent1,4262,089852030256004,059
CaerphillyCefn Fforest2,915Blaenau Gwent3401,3432074093001,870
CaerphillyCrosskeys2,469Caerphilly4139685095058001,584
CaerphillyCrumlin4,355Blaenau Gwent1,0021,205491740363002,793
CaerphillyMaesycwmmer1,657Caerphilly161831534032001,063
CaerphillyNewbridge4,852Blaenau Gwent1,1181,359671830386003,113
CaerphillyPengam2,868Blaenau Gwent4381,11738770171001,841
CaerphillyPenmaen4,014Blaenau Gwent7691,49336800197002,575
CaerphillyPontllanfraith6,399Caerphilly1,0862,493451570325004,106
CaerphillyRisca East4,831Caerphilly7401,965771430175003,100
CaerphillyRisca West3,880Caerphilly9421,21185169081002,488
CaerphillyYnysddu2,922Caerphilly4421,16819590188001,876
 Total56,255 9,82621,2406851,60402,7380036,093

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

Old seat: Merthyr Tydfil and Rhymney

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

Old seat: Merthyr Tydfil and RhymneyTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
Plaid
Votes
MIN
Votes
OTH
Votes
Total
Votes
CaerphillyDarren Valley1,917Merthyr Tydfil and Rhymney89969640056001,160
CaerphillyMoriah3,316Merthyr Tydfil and Rhymney2061,38430540331002,005
CaerphillyNew Tredegar3,669Merthyr Tydfil and Rhymney2691,72417640144002,218
CaerphillyPontlottyn1,405Merthyr Tydfil and Rhymney836061616012900850
CaerphillyTwyn Carno1,804Merthyr Tydfil and Rhymney158801350080001,092
Merthyr TydfilBedlinog2,414Merthyr Tydfil and Rhymney36580180850128001,459
Merthyr TydfilCyfarthfa5,068Merthyr Tydfil and Rhymney6911,895421280308003,064
Merthyr TydfilDowlais5,109Merthyr Tydfil and Rhymney4392,294361010219003,089
Merthyr TydfilGurnos3,894Merthyr Tydfil and Rhymney4071,6773960171002,354
Merthyr TydfilMerthyr Vale2,815Merthyr Tydfil and Rhymney2191,31516400113001,703
Merthyr TydfilPark3,190Merthyr Tydfil and Rhymney4211,2817869081001,930
Merthyr TydfilPenydarren3,994Merthyr Tydfil and Rhymney4301,538122890147002,416
Merthyr TydfilPlymouth3,906Merthyr Tydfil and Rhymney4241,57578900196002,363
Merthyr TydfilTown5,640Merthyr Tydfil and Rhymney5132,0443931540307003,411
Merthyr TydfilTreharris4,705Merthyr Tydfil and Rhymney7201,80925970195002,846
Merthyr TydfilVaynor2,618Merthyr Tydfil and Rhymney63869541120134001,583
 Total55,464 6,07222,4088391,48502,7390033,543

The full details of these calculations are given on the Merthyr Tydfil and Rhymney seat details page. Click on "Show workings".

New seat: Merthyr Tydfil and Rhymney

The new seat of Merthyr Tydfil and Rhymney is made up of the following wards, with the transfer-adjusted votes shown.

New seat: Merthyr Tydfil and Rhymney
DistrictWardElectorate
2017
Old Seat CON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
Plaid
Votes
MIN
Votes
OTH
Votes
Total
Votes
CaerphillyAberbargoed2,520Islwyn921,47628200124001,740
CaerphillyBargoed4,277Caerphilly4072,044246513411002,964
CaerphillyDarren Valley1,838Merthyr Tydfil and Rhymney89969640056001,160
CaerphillyGilfach1,481Caerphilly127686243697800960
CaerphillyHengoed3,617Caerphilly5571,4722210829443002,631
CaerphillyMoriah3,179Merthyr Tydfil and Rhymney2061,38430540331002,005
CaerphillyNelson3,374Caerphilly5901,251897532172002,209
CaerphillyNew Tredegar3,517Merthyr Tydfil and Rhymney2691,72417640144002,218
CaerphillyPontlottyn1,347Merthyr Tydfil and Rhymney836061616012900850
CaerphillySt Cattwg5,400Caerphilly5462,64346788393003,714
CaerphillyTwyn Carno1,729Merthyr Tydfil and Rhymney158801350080001,092
CaerphillyYstrad Mynach3,935Caerphilly6991,131475627441002,401
Merthyr TydfilBedlinog2,314Merthyr Tydfil and Rhymney36580180850128001,459
Merthyr TydfilCyfarthfa4,858Merthyr Tydfil and Rhymney6911,895421280308003,064
Merthyr TydfilDowlais4,897Merthyr Tydfil and Rhymney4392,294361010219003,089
Merthyr TydfilGurnos3,733Merthyr Tydfil and Rhymney4071,6773960171002,354
Merthyr TydfilMerthyr Vale2,698Merthyr Tydfil and Rhymney2191,31516400113001,703
Merthyr TydfilPark3,058Merthyr Tydfil and Rhymney4211,2817869081001,930
Merthyr TydfilPenydarren3,829Merthyr Tydfil and Rhymney4301,538122890147002,416
Merthyr TydfilPlymouth3,744Merthyr Tydfil and Rhymney4241,57578900196002,363
Merthyr TydfilTown5,406Merthyr Tydfil and Rhymney5132,0443931540307003,411
Merthyr TydfilTreharris4,510Merthyr Tydfil and Rhymney7201,80925970195002,846
Merthyr TydfilVaynor2,510Merthyr Tydfil and Rhymney63869541120134001,583
 Total77,771 9,09033,1111,1191,9231184,8010050,162

And these are the implied results for 2017 for the new seat of Merthyr Tydfil and Rhymney.


© 2017 Martin Baxter
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