This is largely for the sake of completeness, since as things stand I doubt the boundary changes will take place, nevertheless I thought I should really update the notional figures for the provisional boundary review.

Calculating how the votes cast at the 2017 election would have translated into seats using the proposed boundaries the Conservatives would have won 298 seats (19 less than currently), Labour would have won 244 (18 less than currently), the Lib Dems would have won 8 (4 less than currently), the SNP 30 (five less than currently), Plaid 2 (2 less than currently). As you can see, the Conservatives and Labour would lose about the same number of seats, but the Conservatives would have been nearer to an overall majority and once you’ve taken away Sinn Fein MPs, may have been able to avoid doing a deal with the DUP.

Regular readers will recall that before the election it looked as if the boundary reviews would have favoured the Tories more – I suspect this change is largely because the 2017 election happened to produce a lot of very marginal seats, and that small boundary changes have flipped some of these in Labour’s favour. If you look at how it affects the swings the two parties would need to win a majority it’s clear that the boundary changes would still help the Tories:

On the the new boundaries the Conservatives would need a lead of 2.8 to get an overall majority, compared to 3.4 currently

On the new boundaries Labour would need to be 3.6 points ahead to become the largest party, compared to 0.8 currently

On the new boundaries Labour would need a lead of 7.8 points to get an overall majority, compared to 7.4 currently

Some of you may be wondering why, if the boundary changes are about evening out the size of constituencies the result is still a system that seems to favour the Conservatives over Labour. This is not a sign of something being afoot – the four boundary commissions are genuinely independent – rather it’s because differently sized constituencies (“malapportionment”) is only one of several factors that can produce a skew in the electoral system, and the current Conservative advantage comes not from seat size, but from the impact of third parties and the Tory vote being more efficiently distributed. For example, when it comes to translating votes into seats huge majorities in safe seats are “wasted” votes. At the 2017 election there were 89 Conservative seats where they got over 60% of the vote, but 115 Labour seats where they got over 60% (and 37 seats where Labour got over 70%). None of this is set in stone of course – up until 2015 the system tended to favour Labour – if a party outperforms in marginal seats it can do better than uniform swing suggests, if it gains votes in safe or unwinnable seats then it would do worse.

The new boundaries are rather irrelevant if they never come into force – when the Boundary Commissions report in Autumn 2018 there then needs to be a vote in both the Commons and the Lords to implement their recommendations. That would have been challenge enough with a majority given that there is every chance of a few Conservative rebels. Without a majority it’s going to be very difficult indeed, especially since the DUP have so far opposed the changes (at the provisional stage the changes were thought to hurt the DUP and benefit Sinn Fein).

Nevertheless, for anyone who wants them notional figures for the 2017 on the provisional boundary recommendations are here.