| Implied MP at 2017: | Jack Dromey (LAB) |
| County/Area: | Birmingham (West Midlands) |
| Electorate: | 80,511 |
| Turnout: | 58.3% |
| Party | Implied 2017 Votes | Implied 2017 Share |
|---|---|---|
| LAB | 27,754 | 59.1% |
| CON | 17,157 | 36.5% |
| LIB | 1,179 | 2.5% |
| Green | 752 | 1.6% |
| MIN | 96 | 0.2% |
| OTH | 16 | 0.0% |
| LAB Majority | 10,597 | 22.6% |
See overview of other seats in West Midlands.
This page shows the detail of the calculations performed to estimate the general election result for 2017 had the new boundaries for Birmingham Erdington and Perry Barr 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.
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.
More details of the calculation formulas are available.
The old seat(s) needed are:
The table shows the transfer-adjusted results for each ward in the old seat of Birmingham Erdington, as well as showing which new seat each ward is in.
| Old seat: Birmingham Erdington | 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 | Erdington | 15,478 | Birmingham Erdington and Perry Barr | 4,102 | 4,218 | 179 | 0 | 149 | 0 | 0 | 0 | 8,648 |
| Birmingham | Kingstanding | 16,007 | Birmingham Erdington and Perry Barr | 3,703 | 5,744 | 107 | 0 | 132 | 0 | 0 | 0 | 9,686 |
| Birmingham | Stockland Green | 15,036 | Birmingham Erdington and Perry Barr | 3,116 | 5,804 | 228 | 0 | 189 | 0 | 0 | 0 | 9,337 |
| Birmingham | Tyburn | 16,031 | Birmingham Erdington and Perry Barr | 3,365 | 5,806 | 237 | 0 | 139 | 0 | 0 | 0 | 9,547 |
| Total | 62,552 | 14,286 | 21,572 | 751 | 0 | 609 | 0 | 0 | 0 | 37,218 | ||
The full details of these calculations are given on the Birmingham Erdington seat details page. Click on "Show workings".
The table shows the transfer-adjusted results for each ward in the old seat of Birmingham Perry Barr, as well as showing which new seat each ward is in.
| Old seat: Birmingham Perry Barr | 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 | Handsworth Wood | 17,301 | West Bromwich | 2,994 | 7,878 | 206 | 0 | 147 | 0 | 99 | 17 | 11,341 |
| Birmingham | Lozells and East Handsworth | 17,558 | Birmingham Ladywood | 1,938 | 10,311 | 196 | 0 | 170 | 0 | 276 | 46 | 12,937 |
| Birmingham | Oscott | 17,483 | Walsall and Oscott | 3,924 | 5,737 | 250 | 0 | 130 | 0 | 121 | 20 | 10,182 |
| Birmingham | Perry Barr | 15,368 | Birmingham Erdington and Perry Barr | 2,871 | 6,182 | 428 | 0 | 143 | 0 | 96 | 16 | 9,736 |
| Total | 67,710 | 11,727 | 30,108 | 1,080 | 0 | 590 | 0 | 592 | 99 | 44,196 | ||
The full details of these calculations are given on the Birmingham Perry Barr seat details page. Click on "Show workings".
| New seat: Birmingham Erdington and Perry Barr | ||||||||||||
| District | Ward | Electorate 2017 | Old Seat | CON Votes | LAB Votes | LIB Votes | UKIP Votes | Green Votes | NAT Votes | MIN Votes | OTH Votes | Total Votes |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Birmingham | Erdington | 15,118 | Birmingham Erdington | 4,102 | 4,218 | 179 | 0 | 149 | 0 | 0 | 0 | 8,648 |
| Birmingham | Kingstanding | 16,933 | Birmingham Erdington | 3,703 | 5,744 | 107 | 0 | 132 | 0 | 0 | 0 | 9,686 |
| Birmingham | Perry Barr | 15,444 | Birmingham Perry Barr | 2,871 | 6,182 | 428 | 0 | 143 | 0 | 96 | 16 | 9,736 |
| Birmingham | Stockland Green | 16,325 | Birmingham Erdington | 3,116 | 5,804 | 228 | 0 | 189 | 0 | 0 | 0 | 9,337 |
| Birmingham | Tyburn | 16,691 | Birmingham Erdington | 3,365 | 5,806 | 237 | 0 | 139 | 0 | 0 | 0 | 9,547 |
| Total | 80,511 | 17,157 | 27,754 | 1,179 | 0 | 752 | 0 | 96 | 16 | 46,954 | ||
And these are the implied results for 2017 for the new seat of Birmingham Erdington and Perry Barr. Please note that the wards used are those of 2015 in order to be consistent with those used by the Boundary Commissions.
© 2024 Electoral Calculus Ltd
Powered by TigerLib (14-Mar-2024 12:19, Py3L, sc5033)