Foyle: New Boundaries 2018 Calculation

Foyle: Overview

 Projection: SF seat 

Implied MP at 2017: Elisha McCallion  (SF)
County/Area: Londonderry (Northern Ireland)
Electorate: 70,934
Turnout: 65.6%

 Implied 2017 VotesImplied 2017 Share
SF18,42239.6%
SDLP18,20039.1%
DUP7,64916.4%
MIN1,4013.0%
OTH8571.8%
UUP200.0%
Green40.0%
SF Majority2220.5%

See overview of other seats in Northern Ireland.

Foyle: 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 Foyle 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 Foyle

The old seat(s) needed are:

Old seat: Foyle

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

Old seat: FoyleTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatUUP
Votes
SDLP
Votes
DUP
Votes
UKIP
Votes
Green
Votes
SF
Votes
MIN
Votes
OTH
Votes
Total
Votes
Derry and StrabaneBallymagroarty2,911Foyle0904660079089551,904
Derry and StrabaneBrandywell2,468Foyle0567450090361371,613
Derry and StrabaneCarn Hill2,237Foyle0685340067046281,463
Derry and StrabaneCaw2,985Foyle06596730057428171,951
Derry and StrabaneCity Walls2,405Foyle0553440087959361,571
Derry and StrabaneClaudy13Glenshane033003009
Derry and StrabaneClondermot2,478Foyle05485580047623141,619
Derry and StrabaneCreggan2,362Foyle0544430086458361,545
Derry and StrabaneCreggan South2,212Foyle0509400081054331,446
Derry and StrabaneCulmore2,954Foyle0904440088560371,930
Derry and StrabaneDrumahoe2,936Foyle06476620056528171,919
Derry and StrabaneEbrington2,762Foyle06096230053126161,805
Derry and StrabaneEglinton2,731Foyle05706510048748301,786
Derry and StrabaneEnagh2,862Foyle05986820051050311,871
Derry and StrabaneFoyle Springs2,225Foyle0690500060468421,454
Derry and StrabaneGalliagh2,891Foyle0886430086659361,890
Derry and StrabaneKilfennan2,911Foyle06436560056027171,903
Derry and StrabaneLisnagelvin2,485Foyle05485600047924151,626
Derry and StrabaneMadam's Bank2,530Foyle0785570068877481,655
Derry and StrabaneNew Buildings2,544Foyle05316070045345281,664
Derry and StrabaneNorthland3,140Foyle0974710085396592,053
Derry and StrabaneShantallow2,470Foyle0756370074050311,614
Derry and StrabaneShantallow East3,004Foyle0920450090061381,964
Derry and StrabaneSheriff's Mountain2,507Foyle0577460091662381,639
Derry and StrabaneSkeoge2,835Foyle0868430084958351,853
Derry and StrabaneSlievekirk1,487Foyle0310354002652616971
Derry and StrabaneSpringtown2,261Foyle0702510061469421,478
Derry and StrabaneVictoria2,717Foyle06006120052226161,776
 Total70,323 018,0907,4000018,2561,37884845,972

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

Old seat: Tyrone West

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

Old seat: Tyrone WestTransfer-adjusted Results
DistrictWardElectorate
2017
New SeatUUP
Votes
SDLP
Votes
DUP
Votes
UKIP
Votes
Green
Votes
SF
Votes
MIN
Votes
OTH
Votes
Total
Votes
Derry and StrabaneArtigarvan2,460Tyrone North372134990880083331,673
Derry and StrabaneBallycolman2,615Tyrone North392265300985188351,778
Derry and StrabaneCastlederg2,423Fermanagh and South Tyrone1161465040982533131,646
Derry and StrabaneDunnamanagh2,439Tyrone North362104940879482321,656
Derry and StrabaneFinn3,052Tyrone North1461856350111,03842172,074
Derry and StrabaneGlenderg2,285Fermanagh and South Tyrone1091384750877732131,552
Derry and StrabaneGlenelly Valley2,191Tyrone North331894450771273291,488
Derry and StrabaneNewtownstewart2,290Fermanagh and South Tyrone1091394750877932131,555
Derry and StrabaneSion Mills2,659Tyrone North12716255301090437151,808
Derry and StrabaneSlievekirk868Foyle2011325204169239590
Derry and StrabaneStrabane North2,500Tyrone North382165070881284331,698
Derry and StrabaneStrabane West2,251Tyrone North341944560773276301,529
Fermanagh and OmaghBeragh2,007Tyrone North88143218042863731,364
Fermanagh and OmaghCamowen2,156Tyrone North642794170765134131,465
Fermanagh and OmaghCoolnagard2,474Tyrone North733214790874539151,680
Fermanagh and OmaghDergmoney1,759Tyrone North522283410653127111,196
Fermanagh and OmaghDromore1,979Fermanagh and South Tyrone89175373066831351,344
Fermanagh and OmaghDrumnakilly2,151Tyrone North95153234046924731,462
Fermanagh and OmaghDrumquin1,983Fermanagh and South Tyrone89176375066831351,347
Fermanagh and OmaghFairy Water1,974Tyrone North88175372066801351,339
Fermanagh and OmaghFintona1,766Fermanagh and South Tyrone79156334066091251,201
Fermanagh and OmaghGortin2,284Tyrone North101163248049982731,553
Fermanagh and OmaghGortrush2,300Tyrone North682984440769336141,560
Fermanagh and OmaghKillyclogher2,136Tyrone North632774130764433131,450
Fermanagh and OmaghNewtownsaville1,798Fermanagh and South Tyrone80159340066201251,222
Fermanagh and OmaghOwenkillew1,839Tyrone North81131199039790621,248
Fermanagh and OmaghSixmilecross2,014Tyrone North89144218042867731,370
Fermanagh and OmaghStrule1,934Tyrone North572513740658330121,313
Fermanagh and OmaghTermon1,625Tyrone North72116176035699621,106
Fermanagh and OmaghTrillick1,797Fermanagh and South Tyrone80159340066191251,221
 Total64,009 2,2525,63511,720042722,05999939643,488

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

New seat: Foyle

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

New seat: Foyle
DistrictWardElectorate
2017
Old Seat UUP
Votes
SDLP
Votes
DUP
Votes
UKIP
Votes
Green
Votes
SF
Votes
MIN
Votes
OTH
Votes
Total
Votes
Derry and StrabaneBallymagroarty2,589Foyle0904660079089551,904
Derry and StrabaneBrandywell2,527Foyle0567450090361371,613
Derry and StrabaneCarn Hill2,301Foyle0685340067046281,463
Derry and StrabaneCaw2,724Foyle06596730057428171,951
Derry and StrabaneCity Walls2,341Foyle0553440087959361,571
Derry and StrabaneClondermot2,644Foyle05485580047623141,619
Derry and StrabaneCreggan2,680Foyle0544430086458361,545
Derry and StrabaneCreggan South2,624Foyle0509400081054331,446
Derry and StrabaneCulmore2,924Foyle0904440088560371,930
Derry and StrabaneDrumahoe2,826Foyle06476620056528171,919
Derry and StrabaneEbrington2,480Foyle06096230053126161,805
Derry and StrabaneEglinton2,670Foyle05706510048748301,786
Derry and StrabaneEnagh2,650Foyle05986820051050311,871
Derry and StrabaneFoyle Springs2,568Foyle0690500060468421,454
Derry and StrabaneGalliagh2,716Foyle0886430086659361,890
Derry and StrabaneKilfennan2,711Foyle06436560056027171,903
Derry and StrabaneLisnagelvin2,537Foyle05485600047924151,626
Derry and StrabaneMadam's Bank2,396Foyle0785570068877481,655
Derry and StrabaneNew Buildings2,735Foyle05316070045345281,664
Derry and StrabaneNorthland2,836Foyle0974710085396592,053
Derry and StrabaneShantallow2,734Foyle0756370074050311,614
Derry and StrabaneShantallow East3,007Foyle0920450090061381,964
Derry and StrabaneSheriff's Mountain2,393Foyle0577460091662381,639
Derry and StrabaneSkeoge2,752Foyle0868430084958351,853
Derry and StrabaneSlievekirk912Tyrone West715622401160189575
Derry and StrabaneSlievekirk1,555Foyle13267382032743116986
Derry and StrabaneSpringtown2,462Foyle0702510061469421,478
Derry and StrabaneVictoria2,640Foyle06006120052226161,776
 Total70,934 2018,2007,6490418,4221,40185746,553

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


© 2017 Martin Baxter
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