The 2015 UK Election wasn’t just a nightmare for the Liberal Democrats and Labour, it was also a disaster for British psephologists. In the closing weeks of the election, all the major pollsters repeatedly predicted a hung parliament, with the Tories and Labour netting approximately the same number of seats. In the wake of Conservatives’ stunning victory, pollsters have been defending their methods and trying to determine how they got the election outcome so wrong.

My initial reaction to the pollsters was sympathetic. 2015 was an usual year: There were more parties than ever with a credible shot of winning seats, the rise of Scottish nationalism was a novel and powerful force, and the number of homes still using ye olde telephone landline was at an unprecedented low. But then I found the video below, showing that in a much simpler election landscape the pollsters muffed the catch in eerily similar fashion in 1992, again failing to predict the Conservative majority that the voters delivered.

I don’t claim to know the full explanation for these polling errors, but this candid admission by Damien Lyons Lowe, head of Survation, suggests that rational herding is part of the problem. This is his description of the poll Survation completed on the eve of the election:

Survation Telephone, Ballot Paper Prompt:
CON 37%
LAB 31%
LD 10
UKIP 11
GRE 5
Others (including the SNP) 6%

Which would have been very close to the final result.

We had flagged that we were conducting this poll to the Daily Mirror as something we might share as an interesting check on our online vs our telephone methodology, but the results seemed so “out of line” with all the polling conducted by ourselves and our peers – what poll commentators would term an “outlier” – that I “chickened out” of publishing the figures – something I’m sure I’ll always regret.