New Seat Details - Hertfordshire South West

This page shows the detail of the calculations performed to estimate the general election result for 2017 had the new boundaries for Hertfordshire South West 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	32,938	60.1%
LAB	12,819	23.4%
LIB	6,491	11.9%
Green	1,486	2.7%
UKIP	1,041	1.9%
CON Majority	20,119	36.7%

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.

Hertfordshire South West: Map

List of old seats forming part of Hertfordshire South West

Old seat: Hemel Hempstead

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

Old seat: Hemel Hempstead				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
Dacorum	Adeyfield East	3,661	Hemel Hempstead	1,514	1,027	120	0	47	0	0	0	2,708
Dacorum	Adeyfield West	3,970	Hemel Hempstead	1,389	1,335	282	0	31	0	0	0	3,037
Dacorum	Apsley and Corner Hall	6,199	Hemel Hempstead	2,477	1,650	266	0	107	0	0	0	4,500
Dacorum	Ashridge	2,095	Hertfordshire South West	1,010	325	57	0	26	0	0	0	1,418
Dacorum	Bennetts End	4,320	Hemel Hempstead	1,644	1,469	180	0	72	0	0	0	3,365
Dacorum	Boxmoor	6,475	Hemel Hempstead	2,550	1,456	359	0	112	0	0	0	4,477
Dacorum	Chaulden and Warners End	6,469	Hemel Hempstead	2,509	1,842	263	0	90	0	0	0	4,704
Dacorum	Gadebridge	3,867	Hemel Hempstead	1,530	1,190	138	0	58	0	0	0	2,916
Dacorum	Grovehill	5,203	Hemel Hempstead	2,208	1,618	214	0	92	0	0	0	4,132
Dacorum	Hemel Hempstead Town	3,822	Hemel Hempstead	1,344	1,354	210	0	41	0	0	0	2,949
Dacorum	Highfield	3,723	Hemel Hempstead	1,348	1,332	318	0	74	0	0	0	3,072
Dacorum	Kings Langley	3,930	Hemel Hempstead	1,762	762	153	0	58	0	0	0	2,735
Dacorum	Leverstock Green	6,748	Hemel Hempstead	2,936	1,525	237	0	99	0	0	0	4,797
Dacorum	Nash Mills	2,350	Hemel Hempstead	899	536	65	0	30	0	0	0	1,530
Dacorum	Watling	4,135	Hemel Hempstead	1,910	784	138	0	27	0	0	0	2,859
Dacorum	Woodhall Farm	3,728	Hemel Hempstead	1,706	1,084	234	0	59	0	0	0	3,083
	Total	70,695		28,736	19,289	3,234	0	1,023	0	0	0	52,282

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

Old seat: Hertfordshire South West

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

Old seat: Hertfordshire South West				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
Dacorum	Aldbury and Wigginton	1,839	Hertfordshire South West	813	308	198	16	59	0	0	0	1,394
Dacorum	Berkhamsted Castle	4,548	Hertfordshire South West	1,995	724	488	41	146	0	0	0	3,394
Dacorum	Berkhamsted East	4,368	Hertfordshire South West	1,818	985	495	39	153	0	0	0	3,490
Dacorum	Berkhamsted West	4,411	Hertfordshire South West	2,043	930	333	38	143	0	0	0	3,487
Dacorum	Bovingdon, Flaunden and Chipperfield	6,276	Hertfordshire South West	3,620	968	348	67	197	0	0	0	5,200
Dacorum	Northchurch	2,127	Hertfordshire South West	1,017	362	146	22	65	0	0	0	1,612
Dacorum	Tring Central	3,822	Hertfordshire South West	1,670	763	430	42	128	0	0	0	3,033
Dacorum	Tring East	2,149	Hertfordshire South West	1,020	375	229	47	31	0	0	0	1,702
Dacorum	Tring West and Rural	4,017	Hertfordshire South West	1,624	752	448	91	130	0	0	0	3,045
Three Rivers	Carpenders Park	1,383	Watford	558	333	102	36	16	0	0	0	1,045
Three Rivers	Chorleywood North and Sarratt	5,848	Hertfordshire South West	2,924	676	252	99	51	0	0	0	4,002
Three Rivers	Chorleywood South and Maple Cross	5,728	Hertfordshire South West	2,619	1,002	664	55	71	0	0	0	4,411
Three Rivers	Dickinsons	5,147	Hertfordshire South West	1,963	1,000	590	113	65	0	0	0	3,731
Three Rivers	Durrants	5,026	Hertfordshire South West	1,812	937	580	118	56	0	0	0	3,503
Three Rivers	Moor Park and Eastbury	4,571	Hertfordshire South West	2,530	525	196	17	39	0	0	0	3,307
Three Rivers	Oxhey Hall and Hayling	2,589	Watford	998	771	256	69	33	0	0	0	2,127
Three Rivers	Penn and Mill End	5,063	Hertfordshire South West	2,082	1,197	608	129	59	0	0	0	4,075
Three Rivers	Rickmansworth Town	5,369	Hertfordshire South West	2,378	990	429	107	67	0	0	0	3,971
Three Rivers	South Oxhey	4,537	Watford	1,643	1,978	286	147	68	0	0	0	4,122
	Total	78,818		35,127	15,576	7,078	1,293	1,577	0	0	0	60,651

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

New seat: Hertfordshire South West

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: Hertfordshire South West
Dacorum	Aldbury and Wigginton	1,846	Hertfordshire South West	813	308	198	16	59	0	0	0	1,394
Dacorum	Ashridge	2,035	Hemel Hempstead	1,010	325	57	0	26	0	0	0	1,418
Dacorum	Berkhamsted Castle	4,495	Hertfordshire South West	1,995	724	488	41	146	0	0	0	3,394
Dacorum	Berkhamsted East	4,620	Hertfordshire South West	1,818	985	495	39	153	0	0	0	3,490
Dacorum	Berkhamsted West	4,617	Hertfordshire South West	2,043	930	333	38	143	0	0	0	3,487
Dacorum	Bovingdon, Flaunden and Chipperfield	6,884	Hertfordshire South West	3,620	968	348	67	197	0	0	0	5,200
Dacorum	Northchurch	2,134	Hertfordshire South West	1,017	362	146	22	65	0	0	0	1,612
Dacorum	Tring Central	4,016	Hertfordshire South West	1,670	763	430	42	128	0	0	0	3,033
Dacorum	Tring East	2,252	Hertfordshire South West	1,020	375	229	47	31	0	0	0	1,702
Dacorum	Tring West and Rural	4,030	Hertfordshire South West	1,624	752	448	91	130	0	0	0	3,045
Three Rivers	Chorleywood North and Sarratt	5,297	Hertfordshire South West	2,924	676	252	99	51	0	0	0	4,002
Three Rivers	Chorleywood South and Maple Cross	5,840	Hertfordshire South West	2,619	1,002	664	55	71	0	0	0	4,411
Three Rivers	Dickinsons	4,940	Hertfordshire South West	1,963	1,000	590	113	65	0	0	0	3,731
Three Rivers	Durrants	4,637	Hertfordshire South West	1,812	937	580	118	56	0	0	0	3,503
Three Rivers	Moor Park and Eastbury	4,378	Hertfordshire South West	2,530	525	196	17	39	0	0	0	3,307
Three Rivers	Penn and Mill End	5,395	Hertfordshire South West	2,082	1,197	608	129	59	0	0	0	4,075
Three Rivers	Rickmansworth Town	5,257	Hertfordshire South West	2,378	990	429	107	67	0	0	0	3,971
	Total	72,673		32,938	12,819	6,491	1,041	1,486	0	0	0	54,775

And these are the implied results for 2017 for the new seat of Hertfordshire South West. 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:	David Gauke (CON)
County/Area:	Hertfordshire (Anglia)
Electorate:	72,673
Turnout:	75.4%

Hertfordshire South West: New Boundaries 2018 Calculation

Hertfordshire South West: Overview

Introduction