The 2017 UK General Election produced another upset for election forecasters and most pollsters (kudos to YouGov for being the only big gun to predict a hung parliament with their new prediction model!). As we have surveyed in our previous text, a vast majority of the poll-based and model-based forecasters, just like with Brexit and the 2015 General Election, got it wrong. They were all estimating a comfortable victory for the Tories. And they would have been right (the Tories got 2.5m more votes than two years ago – see Table), had it not been for Labour’s major upset and an increase of over 3.5m votes since 2015.

Looks like the polls and forecasters underestimated Corbyn’s pulling effect on young voters. The young (under 25) registered in large numbers for this election (more than a million of u-25), and turnout in constituencies with younger voters rose significantly, which most likely benefited Labour.

Let’s look at the numbers:

Source: BBC

Both Labour and the Conservatives had a huge upsurge in vote. For  Labour this was, by number of votes, the best result since Blair in 1997 (13.5m votes). Never since have they had more than 11m votes. For Conservatives it was the best result since Thatcher’s 1987 election (13.7m – and almost the same actually). So who did they take their votes from?

UKIP, most certainly. UKIP had a disastrous night, which is hardly surprising. Their 3.2m votes were most likely split between Tories and Labour about 65:35. This explains the 2.1m more votes for Tories. As for Labour, they most likely got a huge chunk of the 1.5m new voters (large turnout in young, newly-registered voter constituencies), plus almost all Green Party voters. It’s hard to exactly pin down what happened in Scotland. Some are saying that SNP voters switched to the Tories, while others are claiming that they were switching to Labour, which helped the Tories take first place in several constituencies. Both might be true, as the SNP votes probably also split between the two parties, but a bit more in favor of the Tories.

Overall, a fascinating result where the two main parties got more votes than in the past 20 years. After two elections which saw the upsurge of third parties (first the LibDems in 2010 and then UKIP and SNP in 2015), this election re-established the two-party dominance in UK politics. Realignment of the political spectrum a la France? Not quite yet.

Pollster and forecaster performance

Finally, a few more words on failed pre-election predictions.

Source: Wikipedia

In the last week before the elections, only two pollsters were giving Labour 40% – Survation (bolded, as they had the most accurate poll), and Qriously, which was the only one predicting a Labour victory. SurveyMonkey is another one worth mentioning as they too predicted a much narrower lead (at 4%) than most other pollsters who were anchoring Labour down at 35-36%, not believing that large turnout among young voters would prove decisive.

The major forecasters (even more are surveyed here) were way off. In the last week before the vote the consensus was that the election will deliver a comfortable majority for May. Only the above praised YouGov was sceptical and went against the current. The final result wasn’t as close as they predicted, but it was really accurate. Even for LibDems which were dully underestimated by the rest. YouGov’s prediction was only slightly disturbed by the results in Scotland, where Conservatives managed to take some seats away from SNP.

Source: Wikipedia
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