An update on the boundary review. Back in September I published notional figures for the proposed boundaries in England & Wales. I’ve now updated those to include Scotland as well (this is partly because the Scottish boundary Commission published later, but it also took much longer to do – the Scottish Commission are much happier to split wards between constituencies, which probably leads to constituencies that better follow communities… but it makes it trickier to work out notional figures.)

Notional figures for new boundaries for England, Wales and Scotland

The partisan effects in Scotland are no great surprise. The SNP won 56 of Scotland’s 59 seats in 2015, so it was inevitable that most of the losses will be SNP. That aside, on the new boundaries they will be even more dominant. Orkney & Shetland is a protected seat so the sole Liberal Democrat constituency is retained, but Labour and the Conservatives will both see their single Scottish constituency disappear on the new boundaries.

Edinburgh South, the lone Labour seat in Scotland, is split between the new Edinburgh East and Edinburgh South West & Central seats. Both will notionally have an SNP majority of over 4000 – Edinburgh East will be a SNP-Lab marginal, with a SNP majority of 7.9%, Edinburgh SW&C will be a three-way marginal with the SNP in first place, the Conservatives in second place and Labour close behind them.

Dumfriesshire, Clydesdale & Tweeddale, the lone Tory seat in Scotland, mostly goes into Clydesdale & Eskdale, with the rest of the seat split into several much smaller parts. The new Clydesdale & Eskdale seat will have a notional SNP majority of about 5000. On paper the best seat for the Tories will be the new Berwickshire, Roxburgh & Selkirk seat, with a notional SNP majority of only 1.3% (though that’s an increase from 2015).

Now we have notional figures for the whole of Great Britain we can work out national totals and what sort of swings would be needed for parties to win a general election on these boundaries.

The 2015 general election had results of CON 330, LAB 232, LDEM 8, SNP 56, Others 24.

On the proposed boundaries the 2015 general election would have been CON 319, LAB 203, LD 4, SNP 52, Others 22. The Conservatives lose 11 seats, Labour lose 29, the Lib Dems 4 and the SNP 4.

Note that on the boundaries proposed for the abandoned review in the last Parliament the results would have been Con 322, Lab 204, LD 4 and SNP 50 – so this new boundary review is actually marginally worse for the Tories than the one that was blocked before the election.

I should add my normal caveat that these notionals are an accounting exercise – projecting how people voted in each ward, moving them into their new seats and totting up the votes. It does not take into account that some people might have voted differently in 2015 if they’d lived in different seats, for that reason I suspect it may slightly underestimate the Liberal Democrats (and it’s possible that the Greens might actually have saved their seat).

We can also look at what difference the boundaries would make to the leads each party needs to win an election.

Currently the Conservatives need to have a lead of 5.7% to get an overall majority (hence the 6.5% lead they actually got translating into only a tiny majority). On the proposed boundaries the Tories would get an overall majority with a lead of only 1.9%.

In contrast Labour currently need a towering lead of 12.6% to win an overall majority, and the boundary changes would move that target even further away, requiring a lead of 13.5%. To even be the largest party Labour would need a lead over the Conservatives of 4.7% (up from 3.9% on the current boundaries).

(One might reasonably wonder why, if the review makes nearly all the seats the same size, it still leaves the Conservatives in a better position than Labour. This is because different seat sizes is only one part of how votes translate unevenly into seats. The crucial part in explaining the present Conservative advantage is the distribution of the vote and the impact of third parties. The collapse of the Liberal Democrats and the growth of the SNP and UKIP means the system now favours the Conservatives. The Lib Dems are primarily strong in areas that would otherwise be Tory… but now win very few seats, UKIP have largely taken votes from the Tories, but this has not translated into many seats. In contrast the SNP are now utterly dominant in an area that previously returned a large number of Labour MPs. What this means if that if there is a Lib Dem revival or a Labour revival in Scotland the skew towards the Conservatives will unwind.)

These are only provisional recommendations – the boundary commissions will revise them based on the consultation period, so much of the detail will be tweaked before the final recommendations. It’s also far from a certainty that they will actually be implemented when they are complete. Earlier this month Pat Glass MP had a Private Members Bill which if passed would tweak some of the rules of the review, requiring the Commissions to start the process again from scratch and therefore probably delaying it beyond the election. I doubt the Bill will go far – it is nigh on impossible to pass a Private Members Bill in the face of government opposition. However, second reading did highlight some opposition to the boundary changes. Firstly, the DUP spoke against the boundary changes – there had been some speculation around conference season that there had been some sort of deal and the DUP were onside. They are apparently not. Secondly two Conservative MPs (Peter Bone and Steve Double) voted in favour of the Bill. It doesn’t take many rebels to stop the boundary changes progressing…