New Seat Details - Bromsgrove and Droitwich

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

Party	Implied 2017 Votes	Implied 2017 Share
CON	35,862	61.1%
LAB	17,601	30.0%
LIB	3,285	5.6%
Green	1,264	2.2%
UKIP	664	1.1%
CON Majority	18,261	31.1%

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.

Bromsgrove and Droitwich: Map

List of old seats forming part of Bromsgrove and Droitwich

Old seat: Bromsgrove

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

Old seat: Bromsgrove				Transfer-adjusted Results
District	Ward	Electorate 2017	New Seat	CON Votes	LAB Votes	LIB Votes	UKIP Votes	Green Votes	NAT Votes	MIN Votes	OTH Votes	Total Votes
Bromsgrove	Alvechurch South	2,248	Redditch	1,279	305	55	0	21	0	0	0	1,660
Bromsgrove	Alvechurch Village	2,234	Redditch	972	385	76	0	77	0	0	0	1,510
Bromsgrove	Aston Fields	2,492	Bromsgrove and Droitwich	1,086	675	95	0	78	0	0	0	1,934
Bromsgrove	Avoncroft	2,424	Bromsgrove and Droitwich	1,128	511	63	0	24	0	0	0	1,726
Bromsgrove	Barnt Green and Hopwood	2,208	Redditch	1,203	382	71	0	27	0	0	0	1,683
Bromsgrove	Belbroughton and Romsley	5,193	Bromsgrove and Droitwich	2,931	708	109	0	47	0	0	0	3,795
Bromsgrove	Bromsgrove Central	2,363	Bromsgrove and Droitwich	1,115	663	94	0	32	0	0	0	1,904
Bromsgrove	Catshill North	2,208	Bromsgrove and Droitwich	901	684	77	0	68	0	0	0	1,730
Bromsgrove	Catshill South	2,174	Bromsgrove and Droitwich	926	614	61	0	22	0	0	0	1,623
Bromsgrove	Charford	2,318	Bromsgrove and Droitwich	878	995	79	0	30	0	0	0	1,982
Bromsgrove	Cofton	2,142	Redditch	944	353	55	0	57	0	0	0	1,409
Bromsgrove	Drakes Cross	2,489	Redditch	1,233	466	70	0	27	0	0	0	1,796
Bromsgrove	Hagley East	2,044	Bromsgrove and Droitwich	1,121	355	64	0	25	0	0	0	1,565
Bromsgrove	Hagley West	2,680	Bromsgrove and Droitwich	1,427	482	88	0	33	0	0	0	2,030
Bromsgrove	Hill Top	1,778	Bromsgrove and Droitwich	642	635	62	0	20	0	0	0	1,359
Bromsgrove	Hollywood	2,390	Redditch	1,253	418	67	0	24	0	0	0	1,762
Bromsgrove	Lickey Hills	2,242	Bromsgrove and Droitwich	1,139	275	150	0	19	0	0	0	1,583
Bromsgrove	Lowes Hill	2,565	Bromsgrove and Droitwich	1,102	771	85	0	30	0	0	0	1,988
Bromsgrove	Marlbrook	2,395	Bromsgrove and Droitwich	1,147	433	64	0	66	0	0	0	1,710
Bromsgrove	Norton	2,058	Bromsgrove and Droitwich	985	447	67	0	57	0	0	0	1,556
Bromsgrove	Perryfields	1,385	Bromsgrove and Droitwich	517	255	28	0	12	0	0	0	812
Bromsgrove	Rock Hill	2,414	Bromsgrove and Droitwich	893	847	157	0	28	0	0	0	1,925
Bromsgrove	Rubery North	2,507	Birmingham Northfield	840	852	82	0	28	0	0	0	1,802
Bromsgrove	Rubery South	2,563	Birmingham Northfield	923	842	72	0	28	0	0	0	1,865
Bromsgrove	Sanders Park	2,671	Bromsgrove and Droitwich	987	904	81	0	28	0	0	0	2,000
Bromsgrove	Sidemoor	2,530	Bromsgrove and Droitwich	868	957	88	0	31	0	0	0	1,944
Bromsgrove	Slideslow	2,635	Bromsgrove and Droitwich	1,412	530	147	0	75	0	0	0	2,164
Bromsgrove	Tardebigge	2,209	Bromsgrove and Droitwich	1,476	417	71	0	80	0	0	0	2,044
Bromsgrove	Wythall East	2,344	Redditch	1,147	404	68	0	24	0	0	0	1,643
Bromsgrove	Wythall West	2,139	Redditch	1,019	354	141	0	21	0	0	0	1,535
	Total	72,042		33,494	16,919	2,487	0	1,139	0	0	0	54,039

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

Old seat: Worcestershire Mid

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

Old seat: Worcestershire Mid				Transfer-adjusted Results
District	Ward	Electorate 2017	New Seat	CON Votes	LAB Votes	LIB Votes	UKIP Votes	Green Votes	NAT Votes	MIN Votes	OTH Votes	Total Votes
Wychavon	Badsey	2,233	Evesham	1,078	345	57	90	24	0	0	0	1,594
Wychavon	Bengeworth	4,394	Evesham	1,941	801	131	152	113	0	0	0	3,138
Wychavon	Bowbrook	2,339	Evesham	1,101	287	166	25	24	0	0	0	1,603
Wychavon	Bretforton and Offenham	2,203	Evesham	943	324	160	27	21	0	0	0	1,475
Wychavon	Broadway and Wickhamford	3,818	Evesham	1,989	461	97	50	87	0	0	0	2,684
Wychavon	Dodderhill	2,129	Bromsgrove and Droitwich	1,021	280	126	25	21	0	0	0	1,473
Wychavon	Drakes Broughton	1,920	Evesham	1,084	219	47	25	19	0	0	0	1,394
Wychavon	Droitwich Central	1,930	Bromsgrove and Droitwich	718	584	120	75	27	0	0	0	1,524
Wychavon	Droitwich East	4,257	Bromsgrove and Droitwich	1,892	851	235	145	51	0	0	0	3,174
Wychavon	Droitwich South East	4,185	Bromsgrove and Droitwich	2,001	591	236	127	79	0	0	0	3,034
Wychavon	Droitwich South West	3,862	Bromsgrove and Droitwich	1,552	789	256	126	94	0	0	0	2,817
Wychavon	Droitwich West	3,747	Bromsgrove and Droitwich	1,571	1,297	120	63	98	0	0	0	3,149
Wychavon	Evesham North	3,324	Evesham	1,559	880	255	143	108	0	0	0	2,945
Wychavon	Evesham South	3,732	Evesham	2,107	686	144	66	102	0	0	0	3,105
Wychavon	Fladbury	2,214	Evesham	1,090	294	125	26	51	0	0	0	1,586
Wychavon	Great Hampton	2,052	Evesham	853	376	59	80	57	0	0	0	1,425
Wychavon	Hartlebury	2,152	Bromsgrove and Droitwich	1,112	288	110	29	21	0	0	0	1,560
Wychavon	Harvington and Norton	2,048	Evesham	1,115	276	55	25	50	0	0	0	1,521
Wychavon	Honeybourne and Pebworth	2,007	Evesham	1,116	259	44	26	21	0	0	0	1,466
Wychavon	Little Hampton	3,601	Evesham	1,931	744	117	144	100	0	0	0	3,036
Wychavon	Lovett and North Claines	4,230	Bromsgrove and Droitwich	2,321	529	250	52	48	0	0	0	3,200
Wychavon	Norton and Whittington	2,370	Worcester	1,300	272	65	28	23	0	0	0	1,688
Wychavon	Ombersley	1,946	Bromsgrove and Droitwich	993	234	102	22	20	0	0	0	1,371
Wychavon	Pinvin	2,309	Evesham	1,119	364	194	33	26	0	0	0	1,736
Wychavon	The Littletons	2,221	Evesham	1,308	376	76	35	67	0	0	0	1,862
Wychavon	Upton Snodsbury	2,197	Evesham	1,152	233	104	22	19	0	0	0	1,530
	Total	73,420		35,967	12,640	3,451	1,661	1,371	0	0	0	55,090

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

New seat: Bromsgrove and Droitwich

District	Ward	Electorate 2017	Old Seat	CON Votes	LAB Votes	LIB Votes	UKIP Votes	Green Votes	NAT Votes	MIN Votes	OTH Votes	Total Votes
New seat: Bromsgrove and Droitwich
Bromsgrove	Aston Fields	2,634	Bromsgrove	1,086	675	95	0	78	0	0	0	1,934
Bromsgrove	Avoncroft	2,350	Bromsgrove	1,128	511	63	0	24	0	0	0	1,726
Bromsgrove	Belbroughton and Romsley	5,168	Bromsgrove	2,931	708	109	0	47	0	0	0	3,795
Bromsgrove	Bromsgrove Central	2,592	Bromsgrove	1,115	663	94	0	32	0	0	0	1,904
Bromsgrove	Catshill North	2,356	Bromsgrove	901	684	77	0	68	0	0	0	1,730
Bromsgrove	Catshill South	2,210	Bromsgrove	926	614	61	0	22	0	0	0	1,623
Bromsgrove	Charford	2,699	Bromsgrove	878	995	79	0	30	0	0	0	1,982
Bromsgrove	Hagley East	2,131	Bromsgrove	1,121	355	64	0	25	0	0	0	1,565
Bromsgrove	Hagley West	2,764	Bromsgrove	1,427	482	88	0	33	0	0	0	2,030
Bromsgrove	Hill Top	1,849	Bromsgrove	642	635	62	0	20	0	0	0	1,359
Bromsgrove	Lickey Hills	2,155	Bromsgrove	1,139	275	150	0	19	0	0	0	1,583
Bromsgrove	Lowes Hill	2,707	Bromsgrove	1,102	771	85	0	30	0	0	0	1,988
Bromsgrove	Marlbrook	2,329	Bromsgrove	1,147	433	64	0	66	0	0	0	1,710
Bromsgrove	Norton	2,118	Bromsgrove	985	447	67	0	57	0	0	0	1,556
Bromsgrove	Perryfields	1,105	Bromsgrove	517	255	28	0	12	0	0	0	812
Bromsgrove	Rock Hill	2,622	Bromsgrove	893	847	157	0	28	0	0	0	1,925
Bromsgrove	Sanders Park	2,723	Bromsgrove	987	904	81	0	28	0	0	0	2,000
Bromsgrove	Sidemoor	2,646	Bromsgrove	868	957	88	0	31	0	0	0	1,944
Bromsgrove	Slideslow	2,948	Bromsgrove	1,412	530	147	0	75	0	0	0	2,164
Bromsgrove	Tardebigge	2,783	Bromsgrove	1,476	417	71	0	80	0	0	0	2,044
Wychavon	Dodderhill	2,033	Worcestershire Mid	1,021	280	126	25	21	0	0	0	1,473
Wychavon	Droitwich Central	2,103	Worcestershire Mid	718	584	120	75	27	0	0	0	1,524
Wychavon	Droitwich East	4,382	Worcestershire Mid	1,892	851	235	145	51	0	0	0	3,174
Wychavon	Droitwich South East	4,189	Worcestershire Mid	2,001	591	236	127	79	0	0	0	3,034
Wychavon	Droitwich South West	3,890	Worcestershire Mid	1,552	789	256	126	94	0	0	0	2,817
Wychavon	Droitwich West	4,346	Worcestershire Mid	1,571	1,297	120	63	98	0	0	0	3,149
Wychavon	Hartlebury	2,155	Worcestershire Mid	1,112	288	110	29	21	0	0	0	1,560
Wychavon	Lovett and North Claines	4,418	Worcestershire Mid	2,321	529	250	52	48	0	0	0	3,200
Wychavon	Ombersley	1,895	Worcestershire Mid	993	234	102	22	20	0	0	0	1,371
	Total	80,300		35,862	17,601	3,285	664	1,264	0	0	0	58,676

And these are the implied results for 2017 for the new seat of Bromsgrove and Droitwich. Please note that the wards used are those of 2015 in order to be consistent with those used by the Boundary Commissions.

Implied MP at 2017:	Sajid Javid (CON)
County/Area:	Hereford and Worcestershire (West Midlands)
Electorate:	80,300
Turnout:	73.1%

Bromsgrove and Droitwich: New Boundaries 2018 Calculation

Bromsgrove and Droitwich: Overview

Introduction