New Seat Details - Birmingham Hall Green

Party	Implied 2017 Votes	Implied 2017 Share
LAB	40,861	75.2%
CON	8,283	15.3%
LIB	3,980	7.3%
Green	644	1.2%
UKIP	510	0.9%
OTH	28	0.1%
LAB Majority	32,578	60.0%

Introduction

This page shows the detail of the calculations performed to estimate the general election result for 2017 had the new boundaries for Birmingham Hall Green 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.

Birmingham Hall Green: Map

List of old seats forming part of Birmingham Hall Green

Old seat: Birmingham Hall Green

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

Old seat: Birmingham Hall Green				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
Birmingham	Hall Green	18,731	Birmingham Hall Green	3,233	8,195	727	0	136	0	0	0	12,291
Birmingham	Moseley and Kings Heath	17,629	Birmingham Kings Heath	2,339	8,609	932	0	269	0	0	0	12,149
Birmingham	Sparkbrook	18,323	Birmingham Hall Green	965	13,334	657	0	208	0	0	0	15,164
Birmingham	Springfield	19,255	Birmingham Hall Green	1,662	12,005	820	0	218	0	0	0	14,705
	Total	73,938		8,199	42,143	3,136	0	831	0	0	0	54,309

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

Old seat: Birmingham Yardley

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

Old seat: Birmingham Yardley				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
Birmingham	Acocks Green	18,285	Birmingham Hall Green	2,423	7,327	1,776	510	82	0	0	28	12,146
Birmingham	Sheldon	15,778	Birmingham Yardley	2,175	4,380	1,925	414	50	0	0	20	8,964
Birmingham	South Yardley	18,756	Birmingham Yardley	2,040	7,574	2,261	504	80	0	0	23	12,482
Birmingham	Stechford and Yardley North	17,092	Birmingham Hodge Hill	2,185	6,116	2,022	488	67	0	0	29	10,907
	Total	69,911		8,823	25,397	7,984	1,916	279	0	0	100	44,499

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

New seat: Birmingham Hall Green

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: Birmingham Hall Green
Birmingham	Acocks Green	19,812	Birmingham Yardley	2,423	7,327	1,776	510	82	0	0	28	12,146
Birmingham	Hall Green	17,714	Birmingham Hall Green	3,233	8,195	727	0	136	0	0	0	12,291
Birmingham	Sparkbrook	21,855	Birmingham Hall Green	965	13,334	657	0	208	0	0	0	15,164
Birmingham	Springfield	21,192	Birmingham Hall Green	1,662	12,005	820	0	218	0	0	0	14,705
	Total	80,573		8,283	40,861	3,980	510	644	0	0	28	54,306

And these are the implied results for 2017 for the new seat of Birmingham Hall Green. 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:	Roger Godsiff (LAB)
County/Area:	Birmingham (West Midlands)
Electorate:	80,573
Turnout:	67.4%

Birmingham Hall Green: New Boundaries 2018 Calculation

Birmingham Hall Green: Overview