Wednesday, 6 May 2015

Mad Dogs and Englishmen

Hey hey hey!

I know, I know. I still haven’t analysed my results from my last post. I’ll get to it soon, I promise.

In the meantime, the United Kingdom of Great Britain and Northern Ireland will be electing a new house of commons today, so I’m going to take a very superficial look at that right…now.

A Very Superficial Look at That

There are 650 seats. They are elected on a first-past-the-post system. Most polls are predicting a hung parliament.

A Less Superficial Look at That

The following methodology was experimental and, like all good experiments, failed catastrophically. Since the British elections are a special update, this will not be added to the running tally. I know this will be a bad result. Let’s wait and see how bad.

As a rough guide, I’ve made a list of all parties that either won each seat last election or came within 15% of that candidate’s votes. A swing of that magnitude is significantly greater than polling predicts nationally, but also arbitrary.

In many seats, there is only one contender. In fact, the Conservatives were the only ones in 254 seats, with the Democratic Unionist Party picking up another 7 for the right wing. The Liberal Democrats, who joined the Conservatives in a coalition, were the only real contenders in 39 seats. Labour (I’m still getting used to spelling that wrong, which is to say right, which is to say with a ‘u’) gets 203, not counting 15 Labour and Cooperative party seats. Another 15 were picked up by left-wing parties (Plaid Cymru - 3, Scottish National Party - 5, Sinn Fein -4 and Social Democratic and Labour Party - 3). And finally Down North/North Down (if that’s not a contradictory constituency name) is definitively Independent with Lady Sylvia Hermon holding the seat after leaving the Ulster Unionists before the last election. To my knowledge she is contesting again today.

That leaves 116 in doubt, and our tossups are (650/20=17.5) 17 in number.

Add captionSeats determined by having no second candidate within 15% of the vote for the successful candidate

Above seats, expressed as a proportion of the House of Commons

One of these unknowns, Fermanagh and South Tyrone, can be called for Sinn Fein, since their main contender – an Independent – will not run today. More whittling required.

More whittling

I’m keeping it simple due to time constraints, the fact that this is not something I regularly do, and because first past the post is stupid. I’m just going to look at the results for each party in 2005 and 2010 and calculate the swing. I’ll compare that to the national swing. If, for example, the swing from party A to B nationally is twice that in the constituency of Hypotheticalshire North, I’m going to assume Hypotheticalshire North has more rusted-on voters and that the swinging vote is half the national average. Therefore, I’ll halve the national polled swing between A and B and apply that to the 2010 data.

Or, for the cool kids:

where C is the two party* constituency result in year X (or predicted for 2015) and N is the national result in year X (or polled result for 2015).

I applied this to all seats with more a party* within the 15% margin of the winning party (the “competitive parties”). Check the data dump for Table 1.

Now this does lead to some absurdities – swings in excess of 100% being the most obvious. I’ve left these since this is a very rough approximation of a prediction, but it does point out that this algorithm lacks the nuance that it hopes to capture by looking at the size of swings in a seat.
However, the multiplier (the number by which the national swing is multiplied to get the constituency swing) sometimes dips below 0.

This would require the seat to move contrary to the rest of the nation. This is not impossible, but I do not believe in seats that are always contrary to the swing. For this reason negative multipliers are set to 0 in Table 2 (see Data dump)

Now, despite how rough and very, very flawed this is, let’s plug these results into the previous tables.

(Not Honestly a) Prediction


Above seats as a proportion of the House of Commons. A second Conservative-LibDem Coalition would have a majority. A Labour-LibDem Coalition will not.

‘nuf said.

* Hampstead and Kilburn has three competitive parties.

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