New Seat Details - Norwood and Thornton Heath

This page shows the detail of the calculations performed to estimate the general election result for 2017 had the new boundaries for Norwood and Thornton Heath 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	43,012	72.5%
CON	12,141	20.5%
LIB	2,239	3.8%
Green	1,089	1.8%
UKIP	672	1.1%
OTH	168	0.3%
LAB Majority	30,871	52.0%

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.

Norwood and Thornton Heath: Map

List of old seats forming part of Norwood and Thornton Heath

Old seat: Croydon Central

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

Old seat: Croydon Central				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
Croydon	Addiscombe	10,130	Croydon South East	3,385	4,562	273	136	110	0	0	16	8,482
Croydon	Ashburton	10,117	Croydon South East	3,266	3,722	117	144	73	0	0	19	7,341
Croydon	Fairfield	10,688	Croydon South West	3,931	3,797	265	102	95	0	0	12	8,202
Croydon	Fieldway	6,787	Croydon South East	1,695	3,777	27	110	58	0	0	57	5,724
Croydon	Heathfield	9,497	Croydon South East	3,633	2,567	116	124	66	0	0	52	6,558
Croydon	New Addington	6,923	Croydon South East	1,932	3,238	29	111	52	0	0	54	5,416
Croydon	Shirley	10,317	Croydon South East	3,786	2,990	101	139	66	0	0	21	7,103
Croydon	Woodside	10,112	Norwood and Thornton Heath	2,592	5,219	154	173	106	0	0	15	8,259
	Total	74,571		24,220	29,872	1,082	1,039	626	0	0	246	57,085

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

Old seat: Croydon North

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

Old seat: Croydon North				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
Croydon	Bensham Manor	9,553	Norwood and Thornton Heath	1,349	5,396	139	91	111	0	0	18	7,104
Croydon	Broad Green	10,859	Mitcham and Norbury	1,343	6,457	147	93	116	0	0	26	8,182
Croydon	Norbury	9,766	Mitcham and Norbury	1,916	4,909	159	76	115	0	0	26	7,201
Croydon	Selhurst	10,293	Norwood and Thornton Heath	1,390	6,025	208	100	131	0	0	28	7,882
Croydon	South Norwood	10,268	Norwood and Thornton Heath	1,541	5,095	355	108	141	0	0	22	7,262
Croydon	Thornton Heath	9,557	Norwood and Thornton Heath	1,221	5,511	224	110	126	0	0	26	7,218
Croydon	Upper Norwood	10,068	Norwood and Thornton Heath	1,612	4,920	301	90	133	0	0	16	7,072
Croydon	West Thornton	10,159	Mitcham and Norbury	1,476	5,900	123	84	109	0	0	7	7,699
	Total	80,523		11,848	44,213	1,656	752	982	0	0	169	59,620

The full details of these calculations are given on the Croydon North 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".

New seat: Norwood and Thornton Heath

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: Norwood and Thornton Heath
Croydon	Bensham Manor	10,420	Croydon North	1,349	5,396	139	91	111	0	0	18	7,104
Croydon	Selhurst	11,564	Croydon North	1,390	6,025	208	100	131	0	0	28	7,882
Croydon	South Norwood	10,652	Croydon North	1,541	5,095	355	108	141	0	0	22	7,262
Croydon	Thornton Heath	10,589	Croydon North	1,221	5,511	224	110	126	0	0	26	7,218
Croydon	Upper Norwood	10,373	Croydon North	1,612	4,920	301	90	133	0	0	16	7,072
Croydon	Woodside	11,578	Croydon Central	2,592	5,219	154	173	106	0	0	15	8,259
Lambeth	Gipsy Hill	9,745	Dulwich and West Norwood	1,159	5,311	372	0	163	0	0	13	7,018
Lambeth	Knight's Hill	10,422	Dulwich and West Norwood	1,277	5,535	486	0	178	0	0	30	7,506
	Total	85,343		12,141	43,012	2,239	672	1,089	0	0	168	59,321

And these are the implied results for 2017 for the new seat of Norwood and Thornton Heath. 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:	Steve Reed (LAB)
County/Area:	Croydon (London)
Electorate:	85,343
Turnout:	69.5%

Norwood and Thornton Heath: New Boundaries 2018 Calculation

Norwood and Thornton Heath: Overview

Introduction