Rhondda and Llantrisant: New Boundaries 2018 Calculation

Rhondda and Llantrisant: Overview

 Projection: LAB seat 

Implied MP at 2017: Chris Bryant  (LAB)
County/Area: Mid Glamorgan (Wales)
Electorate: 77,905
Turnout: 67.3%

 Implied 2017 VotesImplied 2017 Share
LAB31,93860.9%
Plaid9,42818.0%
CON8,86716.9%
UKIP1,4672.8%
LIB7141.4%
LAB Majority22,51042.9%

See overview of other seats in Wales.

Rhondda and Llantrisant : Political and Demographic indicators

The table below shows some political and demographic numerical indicators for the new Rhondda and Llantrisant 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 Position21° Left10° Left
National Position5° Int3° Int1° Int
EU Leave %54%53%52%
British Identity23%26%29%
Good Health49%47%48%
UK Born96%95%88%
Good Education34%36%39%
Good Job59%46%51%
High SEC61%46%51%
Average Age51.249.648.5
ABC1 Class63%47%53%

Rhondda and Llantrisant ranks #296 for "Leave", #591 for "Right" and #440 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

Rhondda and Llantrisant: 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 Rhondda and Llantrisant 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 Rhondda and Llantrisant

The old seat(s) needed are:

Old seat: Ogmore

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

Old seat: OgmoreTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
Plaid
Votes
MIN
Votes
OTH
Votes
Total
Votes
BridgendAberkenfig1,538Ogmore and Aberavon39344813430113001,010
BridgendBettws (Ogmore)1,689Ogmore and Aberavon248769127063001,108
BridgendBlackmill1,882Ogmore and Aberavon1949292044047001,234
BridgendBlaengarw1,357Ogmore and Aberavon10173501104400891
BridgendBryncethin1,012Ogmore and Aberavon189389431203100664
BridgendBryncoch1,703Ogmore and Aberavon2897047135020001,119
BridgendCaerau5,308Ogmore and Aberavon8652,222361990162003,484
BridgendCefn Cribwr1,126Bridgend and Vale of Glamorgan West14055601502800739
BridgendFelindre2,105Ogmore and Aberavon39782410737017001,382
BridgendHendre3,134Ogmore and Aberavon9031,0211779038002,058
BridgendLlangeinor943Ogmore and Aberavon724937704000619
BridgendLlangynwyd2,312Ogmore and Aberavon3278050540332001,518
BridgendMaesteg East3,622Ogmore and Aberavon3731,6527950252002,379
BridgendMaesteg West4,402Ogmore and Aberavon5771,83649820345002,889
BridgendNant-y-moel1,776Ogmore and Aberavon3976362257053001,165
BridgendOgmore Vale2,367Ogmore and Aberavon5678143692045001,554
BridgendPenprysg2,383Ogmore and Aberavon6088331487022001,564
BridgendPontycymmer1,896Ogmore and Aberavon1949481020072001,244
BridgendSarn1,854Ogmore and Aberavon250889032045001,216
BridgendYnysawdre2,561Ogmore and Aberavon39598210350260001,682
Rhondda Cynon TafBrynna2,901Ogmore and Aberavon4291,22726310191001,904
Rhondda Cynon TafGilfach Goch2,625Ogmore and Aberavon2871,2646840063001,722
Rhondda Cynon TafLlanharan2,632Ogmore and Aberavon50492727420228001,728
Rhondda Cynon TafLlanharry2,813Rhondda and Llantrisant4201,1521320242001,847
Rhondda Cynon TafPont-y-clun707 22916452504100464
Rhondda Cynon TafTalbot Green12 430101009
 Total56,660 9,35223,2225901,23402,7950037,193

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

Old seat: Pontypridd

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

Old seat: PontypriddTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
Plaid
Votes
MIN
Votes
OTH
Votes
Total
Votes
Rhondda Cynon TafBeddau3,140Rhondda and Llantrisant4561,35156430163002,069
Rhondda Cynon TafChurch Village3,794Cynon Valley and Pontypridd6541,50456300255002,499
Rhondda Cynon TafGraig (Pontypridd)1,855Cynon Valley and Pontypridd24677953180127001,223
Rhondda Cynon TafHawthorn2,699Cynon Valley and Pontypridd297946112630359001,777
Rhondda Cynon TafLlanharry94 104111090062
Rhondda Cynon TafLlantrisant Town3,665Rhondda and Llantrisant6171,46082260228002,413
Rhondda Cynon TafLlantwit Fardre4,602Cynon Valley and Pontypridd1,4091,24980600234003,032
Rhondda Cynon TafPont-y-clun5,297Rhondda and Llantrisant1,5451,340971710336003,489
Rhondda Cynon TafPontypridd Town2,132Cynon Valley and Pontypridd420681138600104001,403
Rhondda Cynon TafRhondda3,510Cynon Valley and Pontypridd6141,317491090223002,312
Rhondda Cynon TafRhydfelen Central / Ilan3,370Cynon Valley and Pontypridd2121,61383480264002,220
Rhondda Cynon TafTaffs Well2,788Cardiff West3711,05751280330001,837
Rhondda Cynon TafTalbot Green1,972Rhondda and Llantrisant5426024645064001,299
Rhondda Cynon TafTon-teg3,022Cynon Valley and Pontypridd6561,010159620104001,991
Rhondda Cynon TafTonyrefail East4,460Rhondda and Llantrisant8021,622891000324002,937
Rhondda Cynon TafTonyrefail West4,800Rhondda and Llantrisant6911,846361020486003,161
Rhondda Cynon TafTrallwng2,841Cynon Valley and Pontypridd424871423330120001,871
Rhondda Cynon TafTreforest3,900Cynon Valley and Pontypridd4711,552327320187002,569
Rhondda Cynon TafTyn-y-nant2,626Rhondda and Llantrisant2171,26126410185001,730
 Total60,567 10,65422,1021,9641,07204,1020039,894

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

Old seat: Rhondda

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

Old seat: RhonddaTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatCON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
Plaid
Votes
MIN
Votes
OTH
Votes
Total
Votes
Rhondda Cynon TafCwm Clydach2,028Rhondda and Llantrisant909142550262001,323
Rhondda Cynon TafCymmer3,996Rhondda and Llantrisant2331,8285440496002,606
Rhondda Cynon TafFerndale3,034Rhondda and Llantrisant3261,17720850370001,978
Rhondda Cynon TafLlwyn-y-pia1,638Rhondda and Llantrisant727445170230001,068
Rhondda Cynon TafMaerdy2,295Rhondda and Llantrisant591,1592330244001,497
Rhondda Cynon TafPen-y-graig4,033Rhondda and Llantrisant2611,71222570577002,629
Rhondda Cynon TafPentre3,791Rhondda and Llantrisant3361,37440640658002,472
Rhondda Cynon TafPorth4,325Rhondda and Llantrisant3731,7118690659002,820
Rhondda Cynon TafTonypandy2,722Rhondda and Llantrisant1701,1554750370001,774
Rhondda Cynon TafTrealaw2,933Rhondda and Llantrisant1721,3425620332001,913
Rhondda Cynon TafTreherbert4,159Rhondda and Llantrisant2031,58538700815002,711
Rhondda Cynon TafTreorchy5,588Rhondda and Llantrisant5002,0053310001,005003,643
Rhondda Cynon TafTylorstown3,301Rhondda and Llantrisant1531,5826530358002,152
Rhondda Cynon TafYnyshir2,411Rhondda and Llantrisant1331,04413290353001,572
Rhondda Cynon TafYstrad4,259Rhondda and Llantrisant2531,76472670620002,776
 Total50,513 3,33421,09627588007,3490032,934

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

New seat: Rhondda and Llantrisant

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

New seat: Rhondda and Llantrisant
DistrictWardElectorate
2017
Old Seat CON
Votes
LAB
Votes
LIB
Votes
UKIP
Votes
Green
Votes
Plaid
Votes
MIN
Votes
OTH
Votes
Total
Votes
Rhondda Cynon TafBeddau3,090Pontypridd4561,35156430163002,069
Rhondda Cynon TafCwm Clydach1,974Rhondda909142550262001,323
Rhondda Cynon TafCymmer3,889Rhondda2331,8285440496002,606
Rhondda Cynon TafFerndale2,953Rhondda3261,17720850370001,978
Rhondda Cynon TafLlanharry2,940Ogmore4301,1932330251001,909
Rhondda Cynon TafLlantrisant Town3,590Pontypridd6171,46082260228002,413
Rhondda Cynon TafLlwyn-y-pia1,594Rhondda727445170230001,068
Rhondda Cynon TafMaerdy2,234Rhondda591,1592330244001,497
Rhondda Cynon TafPen-y-graig3,925Rhondda2611,71222570577002,629
Rhondda Cynon TafPentre3,690Rhondda3361,37440640658002,472
Rhondda Cynon TafPont-y-clun5,888Pontypridd1,7741,5041021960377003,953
Rhondda Cynon TafPorth4,209Rhondda3731,7118690659002,820
Rhondda Cynon TafTalbot Green1,936Pontypridd5466054646065001,308
Rhondda Cynon TafTonypandy2,649Rhondda1701,1554750370001,774
Rhondda Cynon TafTonyrefail East4,215Pontypridd8021,622891000324002,937
Rhondda Cynon TafTonyrefail West4,620Pontypridd6911,846361020486003,161
Rhondda Cynon TafTrealaw2,854Rhondda1721,3425620332001,913
Rhondda Cynon TafTreherbert4,048Rhondda2031,58538700815002,711
Rhondda Cynon TafTreorchy5,438Rhondda5002,0053310001,005003,643
Rhondda Cynon TafTylorstown3,213Rhondda1531,5826530358002,152
Rhondda Cynon TafTyn-y-nant2,465Pontypridd2171,26126410185001,730
Rhondda Cynon TafYnyshir2,346Rhondda1331,04413290353001,572
Rhondda Cynon TafYstrad4,145Rhondda2531,76472670620002,776
 Total77,905 8,86731,9387141,46709,4280052,414

And these are the implied results for 2017 for the new seat of Rhondda and Llantrisant.


© 2017 Martin Baxter
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