New Seat Details - Dulwich and Sydenham

This page shows the detail of the calculations performed to estimate the general election result for 2017 had the new boundaries for Dulwich and Sydenham 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
LAB	36,742	66.2%
CON	12,359	22.3%
LIB	4,357	7.8%
Green	1,331	2.4%
UKIP	385	0.7%
OTH	344	0.6%
LAB Majority	24,383	43.9%

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.

Dulwich and Sydenham: Map

List of old seats forming part of Dulwich and Sydenham

Old seat: Camberwell and Peckham

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

Old seat: Camberwell and Peckham				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
Southwark	Brunswick Park	8,656	Camberwell and Peckham	755	4,818	427	0	188	0	0	39	6,227
Southwark	Camberwell Green	9,134	Camberwell and Peckham	716	5,549	338	0	191	0	0	48	6,842
Southwark	Faraday	6,882	Bermondsey and Old Southwark	573	4,247	245	0	136	0	0	44	5,245
Southwark	Livesey	8,669	Camberwell and Peckham	694	5,288	356	0	161	0	0	44	6,543
Southwark	Nunhead	9,269	Camberwell and Peckham	756	5,040	355	0	182	0	0	46	6,379
Southwark	Peckham	9,281	Camberwell and Peckham	653	5,692	284	0	179	0	0	44	6,852
Southwark	Peckham Rye	9,463	Dulwich and Sydenham	1,194	4,394	482	0	194	0	0	22	6,286
Southwark	South Camberwell	8,471	Camberwell and Peckham	921	4,278	452	0	181	0	0	34	5,866
Southwark	The Lane	10,550	Camberwell and Peckham	1,088	5,359	473	0	213	0	0	37	7,170
	Total	80,375		7,350	44,665	3,412	0	1,625	0	0	358	57,410

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

Old seat: Dulwich and West Norwood

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

Old seat: Dulwich and West Norwood				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
Lambeth	Coldharbour	10,101	Brixton and Vauxhall	862	6,794	421	0	197	0	0	81	8,355
Lambeth	Gipsy Hill	9,064	Norwood and Thornton Heath	1,159	5,311	372	0	163	0	0	13	7,018
Lambeth	Herne Hill	9,975	Streatham and Brixton Hill	1,113	5,724	580	0	222	0	0	55	7,694
Lambeth	Knight's Hill	8,629	Norwood and Thornton Heath	1,277	5,535	486	0	178	0	0	30	7,506
Lambeth	Thurlow Park	8,776	Streatham and Brixton Hill	1,719	4,518	495	0	176	0	0	13	6,921
Southwark	College	8,312	Dulwich and Sydenham	1,712	3,781	375	0	140	0	0	10	6,018
Southwark	East Dulwich	9,127	Dulwich and Sydenham	1,016	4,025	1,023	0	176	0	0	12	6,252
Southwark	Village	8,592	Dulwich and Sydenham	2,082	3,408	724	0	156	0	0	9	6,379
	Total	72,576		10,940	39,096	4,476	0	1,408	0	0	223	56,143

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

Old seat: Lewisham West and Penge

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

Old seat: Lewisham West and Penge				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
Bromley	Clock House	10,932	Beckenham	2,690	4,272	604	109	155	0	0	29	7,859
Bromley	Crystal Palace	7,783	Beckenham	1,143	4,198	505	87	145	0	0	25	6,103
Bromley	Penge and Cator	11,248	Beckenham	2,059	5,807	455	119	180	0	0	30	8,650
Lewisham	Bellingham	9,019	Dulwich and Sydenham	1,412	5,452	285	68	136	0	0	73	7,426
Lewisham	Forest Hill	9,201	Dulwich and Sydenham	1,490	4,942	690	89	184	0	0	78	7,473
Lewisham	Perry Vale	9,807	Dulwich and Sydenham	1,618	5,454	432	112	179	0	0	71	7,866
Lewisham	Sydenham	9,663	Dulwich and Sydenham	1,835	5,286	346	116	166	0	0	69	7,818
	Total	67,653		12,247	35,411	3,317	700	1,145	0	0	375	53,195

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

New seat: Dulwich and Sydenham

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: Dulwich and Sydenham
Lewisham	Bellingham	10,177	Lewisham West and Penge	1,412	5,452	285	68	136	0	0	73	7,426
Lewisham	Forest Hill	10,240	Lewisham West and Penge	1,490	4,942	690	89	184	0	0	78	7,473
Lewisham	Perry Vale	10,781	Lewisham West and Penge	1,618	5,454	432	112	179	0	0	71	7,866
Lewisham	Sydenham	10,716	Lewisham West and Penge	1,835	5,286	346	116	166	0	0	69	7,818
Southwark	College	8,355	Dulwich and West Norwood	1,712	3,781	375	0	140	0	0	10	6,018
Southwark	East Dulwich	8,681	Dulwich and West Norwood	1,016	4,025	1,023	0	176	0	0	12	6,252
Southwark	Peckham Rye	9,370	Camberwell and Peckham	1,194	4,394	482	0	194	0	0	22	6,286
Southwark	Village	8,856	Dulwich and West Norwood	2,082	3,408	724	0	156	0	0	9	6,379
	Total	77,176		12,359	36,742	4,357	385	1,331	0	0	344	55,518

And these are the implied results for 2017 for the new seat of Dulwich and Sydenham. 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:	Ellie Reeves (LAB)
County/Area:	Lewisham (London)
Electorate:	77,176
Turnout:	71.9%

Dulwich and Sydenham: New Boundaries 2018 Calculation

Dulwich and Sydenham: Overview

Introduction