Today, the House of Commons Library released a Briefing Paper, Constituency boundary reviews and the number of MPs.
This paper announces the commencement of a review of parliamentary constituencies to be concluded in 2018. The Briefing Paper states that,
The Boundary Commissions launched their reviews on 24 February 2016. They confirmed the electoral quota for the 2018 Review is 74,769. This means constituencies must have an electorate between 71,031 and 78,507.
An earlier House of Commons Library Briefing Paper has the sizes of constituency electorates the 2010 general election. Looking through the list, one quickly sees that some are in the high 80,000’s, while others are in the mid 40,000’s.
Hence, again from today’s Briefing Paper, an explanation of the reason for the change,
The new rules were intended to create equally sized constituencies, so that one vote counts for approximately the same, no matter in which constituency it was cast.
Lewis Baston, political analyst in The Times, in Bonfire of the Boundaries, has created this table of how changes in share of seats might affect political parties,
UPDATE: The new boundary review gets going in UK Polling Report.