UK - Alternate Coloring

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Northern Ireland isn't covered by the UK Ordnance Survey. To be fair to the Electoral Office for Northen Ireland, they probably have more dodgy electoral incidents to monitor than their peers do. They published shapefiles for the latest, abortive revision of boundaries that ended in 2013.

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The data are out there, but the map is rather difficult to produce, because some of the constituencies were only used at the 1945 election and their boundaries are not well documented on the WWW. I'm sure someone on this forum has done it. In the interim, here is a 1945 majorities map, shaded by a continuous rather than discrete scale:



Image created with the UK-Elect software and FWS Craig's results and boundaries guides. Boundaries are correct in approximately 98% of cases.

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That's exactly right. Swing was designed to summarise behaviour in a two-party system, back in the days when England gave 97% of votes to LabCon. It's not great when a third party can intervene, and it's going to give very strange results at the next general election.

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What would a better version of swing look like?

Possibly an index of winnability/safety.

Say party W is the winner at this election, and party N was the next-highest party after W at the previous election (i.e. N either won or came second after W).

The change in winnability/safety would be the average of W's current majority and the gap between N and W at the previous election. It's not quite an average of majorities, because W could have previously finished third, fourth, or nowhere.

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A little late, I realize, but finally found a set of 2017 vote figures that seemed final (and didn't mysteriously contain 2015 results in some constituencies!), so here's a map for last summer's vote.

Electoral Commission data still off? (Edit: I haven't followed this thread, why is St Ives so dark in left-hand map?)

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There are still some unreconciled differences even in official sources, like whether Labour in Milton Keynes South won 28,987 votes (Milton Keynes Council and Electoral Commission) or 28,927 (House of Commons Library provisional figures).

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Here's a swing map for 2017:
If one was to characterize these differences, it would be that the most longtime loyal Labour areas either swung Tory or at least very little to Labour, while the areas that haven't been as Labour-friendly or at least haven't been for as long did swing very hard. Even when the Tories were forecast to win very heavily, such a swing difference seemed to be expected.

Many of them are heartlands of White English ethnics, often where culture and immigration are or have been significant vote swingers. The Black Country, the Thames Estuary, the east coast, and more recently there was a very bad conspiracy to hurt children concentrated among some British Pakistanis in South Yorkshire. What I can't explain: Tyne Tees land (formerly known as the North-East Euroregion). The other phenomenon is LD collapse from 2nd or 3rd in a handful of constituencies where they had built a vote among natural Tories.

Why this all happened to help the incumbent Tories in 2017 is another question. My guess is that Ukip did unusually well among those voters in 2015, and they fell back to their "natural" home (since 1970).