Post-mortem for the pollsters

But while Shakespeare went for a mea culpa on Twitter – ‘A terrible night for us pollsters. I apologise for a poor performance. We need to find out why’ others were more robust in their defence of the polls.

Andrew Hawkins, ComRes chairman argued that the pollsters were accurate measuring vote share but were not in the business of forecasting seats saying there was “not a systemic problem” with polling.

“Exit polls are a calculation of seats whereas the pre-election polls are a calculation of vote share. All ComRes election vote shares were in the margin of error so statistically it’s where it should be. So the problem has not been with measuring vote share –although some voting intention was more accurate than others– what has changed is the relationship with vote share and number of seats. UKIP gets 12% share and still only one seat; conservatives get 35 – 37% and it can be the difference between a majority and forming a coalition,” said Hawkins.

He did concede that a collective effort was needed from academics, the media and pollsters to make sure polling share is accurately interpreted.

But Mike Smithson, polling analyst and independent political blogger was scathing of the pollsters’ performance. “It was an absolutely terrible night for the pollsters. It was quite shocking that they all went to such great lengths to have final polls with fieldwork going right up to late evening on Wednesday – with the polls only published yesterday – in order to try and detect any late swing, and they didn’t detect it. They found the swing going to Labour, and of course that was not what happened. That is just extraordinary.

“I think there’ll be lots of lessons to be learned here – across sampling, methodology, weightings. I can see a complete re-look and re-examination of how we do political polling.”

Deborah Mattinson, co-founder of BritainThinks said that while the margin of error argument might stand up if the polls were all varying, it didn’t when they were so close.

“Political polling is an art rather than a science,” she said. “Someone said to me: ‘we pollsters would rather be wrong together than right on our own’. In this instance they were grouping together and wrong. Lord Ashcroft spent so much money on marginals and that was also wrong. The national picture is explainable with late surge, silent Tories etc, but I don’t know how you explain getting it so wrong at a constituency level – other than a late surge,” she added.

James Myring, director, BDRC Continental pointed to other methodological factors: “It does seem as if the polls got it wrong. Labour and the Conservatives were neck-and-neck in the polls at around 34% each, while the actual results show a clear lead for the Conservatives with 37% of the vote compared to Labour’s 31%.

“But there is more than one way to skin a cat…as researchers we don’t merely have the option of asking people how they would vote but also asking them how others would vote.  This is the wisdom method.  ICM conducted a wisdom poll, and this put Tories on 35% and Labour on 32%. Not quite the final outcome, but correct on the key point of showing a clear gap between the two major parties.”