Tuesday, 30 May 2017

The swingers

Kaleb has left a comment on a previous post, asking what constituencies my model predicted to change hands, with respect to the 2015 election. This is not too difficult to do, given the wealth of results and quantities that can be computed, once the posterior distributions are estimated.

Basically, what I have done is to compute, based on the "possible futures" simulated by the model, the probability that the parties win each of the 632 seats in England, Wales and Scotland. Many of them seem to be very safe seats $-$ I think this is consistent with current political knowledge, although in an election like this possibly more can change...

Anyway, using the very latest analysis (as of today, 30th May and based on all polls published so far, but discounting older ones), there are 39 seats that are predicted to change hands. The following graph shows the predicted distribution of the probability of winning each of those seats, together of an indication of who won in 2015.

Of course, Labour are the big losers (there are many of the 39 constituencies that were Labour in 2015, but are predicted to swing to some other party in 9 days time). Conversely, the Tories are the big winners and most often, when they do, they are predicted to win that seat with a very large probability. There aren't very many real 50:50s $-$ a couple, I'd say, where the results are predicted to be rather uncertain. 

Incidentally, as of today, this is the distribution of seats predicted by the model.

                mean        sd 2.5% median 97.5%
Conservative 359.467 5.4492757  351    358   371
Labour       209.276 5.3613961  198    211   218
UKIP           0.000 0.0000000    0      0     0
Lib Dem       14.699 2.1621920   10     15    19
SNP           48.055 2.7271620   42     48    52
Green          0.000 0.0000000    0      0     0
PCY            0.503 0.8286602    0      0     3
Other          0.000 0.0000000    0      0     0

Labour are continuing to close the gap on the Tories, but are still a long way out. I'm curious to see what last night not-a-debate did to the polls...

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