What do the boundary changes mean?

The Boundary Commission(s) for England, Scotland and Wales have all respectively published their initial boundary proposals (map below). The intentions of these proposals are to see an equal number of electors in all seats across the United Kingdom (no less than 71,000) with the hope that they will be used for the 2020 General Election. These proposals are likely to be altered and revised come the Autumn of 2017, however.

At the last election, which used different boundaries, the Conservatives won 330 seats and Labour 232. The new draft constituencies raise the question of how the country may have looked were 2015 fought on these proposed boundaries. This is to gauge for 2020 how far, for example, Labour may need to climb to clinch Downing Street (on the old boundaries they would need to make a net gain of 93 seats), or how fatter or thinner the current 12 seat Tory majority may be.

To our knowledge there have been only two attempts at number crunching to gauge the notional results of these new boundaries. The calculations by Anthony Wells and Martin Baxter both suggest that the notional results on these new boundaries are to give the Conservatives an enlarged majority. Putting it in percentage terms, on the old boundaries, the Tories took 50.8% of seats (330/650), on the new they would have took around 53% (Wells: 319/600, Baxter: 316/600).

How notional results are calculated for these new constituencies involve assumptions made through aggregating the ward results of local council elections. While not accurate to the single vote – and those with very close notional results ought to be judged as tossups/too-close-to-call, most of the time they do provide a satisfactory indicator of where support for each party is concentrated and how that constituency – in the aggregate – is composed. It ought to be said that notional figures are a simple aggregate exercise and don’t account for the potential reality that electors may have voted otherwise in the event a certain candidate/personality was on the ballot paper.

The wards included to compile East Thanet, for example, show a seat with a result closer between the Conservatives and UKIP than South Thanet, of which the seat broadly replaces. It would therefore be reasonable to suggest that East Thanet ought to be regarded as a tossup. The notionals by Anthony Wells make it Conservative; Martin Baxter’s make it UKIP.

PartyAnthony WellsMartin Baxter
Liberal Democrat44
Plaid Cymru33
Other parties1818

On the notional results:-

What of the Greens?

The redrawing of the boundaries in Brighton sees Green support split between Brighton North and Brighton Central & Hove, whereas on the old boundaries it was mostly concentrated in Brighton Pavilion. The new Brighton North seat, which replaces much of Caroline Lucas’ Pavilion constituency, sees the addition of Tory leaning wards such as Hove Park and Withdean, notionally turning the constituency in the aggregate blue instead of green. It should be stressed, though, that this is a purely arithmetical exercise. It does not account for the potential reality that electors may have voted differently depending on the constituency they could vote in.

What of the Liberal Democrats?

On the proposed boundaries the Lib Dems are notionally set to defend four seats, down from eight: Orkney & Shetland, Ceredigion, Westmorland & Lonsdale and North Norfolk.

Southport and Carshalton & Wallington go notionally Conservative; Leeds North West and Sheffield Hallam & Stocksbridge go Labour. The redrawn Cambridge seat, like East Thanet, looks set to prove an interesting toss-up with a notional result of Labour leading the Lib Dems by just 200 votes.

The proposed boundaries, notionals:

Notional results sourecd via Anthony Wells, ukpollingreport.co.uk