Opinion polls on voting intention are a snapshot of how the political parties current support stacks up. They aren’t an attempt to predict the next election, they aren’t even really an attempt to show how people would vote in that mythical “general election tomorrow” – there isn’t a general election tomorrow, and if there was there would have just been four weeks of electioneering, the parties would all have permanent leaders, wouldn’t be conducting policy reviews and so on. They are just a snapshot.

That doesn’t stop us all translating poll ratings into general election results – “just for a bit of fun” as Peter Snow used to say. There is a real purpose to it as well – the Conservative party cannot afford to rest on its laurels with a lead of a couple of pencentage points, because when translated into seats the Labour party would still be the largest party in the Commons.

Before the next election though the Parliamentary boundaries will change in England and Wales, with consequential changes to the amount of votes the parties need to secure a majority. Whenever the boundaries change Michael Thrasher and Colin Rallings of the University of Plymouth calculate notional votes for the new boundaries, so the media can talk about swings and suchlike. Their figures won’t be available for some months yet though so, as my regular readers will know, last year I produced some early estimates of the effect this would have on the number of seats held by each party. Since then I’ve finished poducing notional figures and the pdf below has list of the parties’ target seats under the new boundaries, some of the most significant changes and a simple swing calculator.

The bottom line is that under the new boundaries Labour would have won 10 seats fewer at the last election, the Conservatives 14 seats more and the Lib Dems one seat more. On the new boundaries it will be more difficult for Labour to retain their majority at the next election (a swing of just 1.5% to the Tories will rob them of a majority, compared to 2.2% on the present boundaries) making a hung Parliament more likely. It will be slightly easier for the Conservatives to gain a majority, but not much easier (they will need a 7.1% swing, compared to 7.4% on the old boundaries).

Let me know if you spot any mistakes, and I’ll repeat two of the caveats in the guide – firstly, the calculation is based just on local and general election results, the overall picture should be good, but in individual seats it’s no substitute for someone with really sound local knowledge. Secondly, notional boundaries make the assumption that people’s voting behaviour doesn’t change – in really if you move someone from a rock solid safe Labour seat to a Con/LD marginal, there’s every chance they might change their voting behaviour.

pdf Download guide to new Parliamentary Boundaries


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