Polling Failure in the UK
By 
As the occasional (charitably) LGM Senior British Correspondent, I’m going to weigh in with a series of thoughts on the British General Election last week. Cards on table: one of several reasons for my extended sabbatical(*) from LGM has been my active involvement, time permitting, in the Labour Party campaign here in Plymouth.
When I walked into the Plymouth Guildhall Thursday night around 10:15 to participate in the counting of the ballots as a count agent for my Constituency Labour Party, following 14 hours on the campaign trail, I was immediately confronted with the exit poll conducted by several pollsters for several media organisations. The poll was a shock as it was inconsistent with the narrative created by the last year of public polling released by the major houses. All the major polls, and the five or six seat projection models, suggested a hung parliament. The largest single party in this new parliament would likely be the Conservatives, but they would only have anywhere from five to 15 more seats than Labour, and the maths suggested there was no way the Tories could form a stable minority government, let alone a coalition:
The exit poll will be out very shortly, and then we’ll have a good idea (or a false one). But first, here’s the game. No one is going to win an overall majority, so it’s all about who can cobble together 323 seats – the number needed for a majority – by banding together with other parties.
Second, Labour seem the most likely to win that game. May2015’s Poll of Polls, which has averaged all the latest polls since September, has finally finished adding numbers up. It’s conclusion? The Tories are going to win 33.8 per cent of the vote, and Labour are going to win 33.7.
This was the narrative the pollsters stood by, and the narrative that those of us academics called upon by the media used as the foundation for discussion (with our own various caveats). Quite obviously this was wrong, and I’m plastered all over the media both in Devon and the Southwest of England as getting it very wrong.
For the 2015 General Election, we had access to considerably more, and richer, data than in elections past. It felt like an embarrassment of riches, and a certain hubris resulted. In addition to the national level polling, Lord Ashcroft released around 130 constituency level polls of marginal seats. These, with the expected N of around 1000, for the first time allowed us to understand how the national numbers and trends were being reflected at the constituency level not only occasionally, but systematically. We were in a position where we could finally bury the swingometer based on the mythical uniform national swing.
The interesting academic question from this election is why polling in the UK failed as bad (if not worse) than it did in 1992. At this early point, we don’t know, and anybody offering a definitive explanation is taking a significant risk. There are working theories and interesting questions; four can be found here from YouGov, ICM, Populus, and ComRes. Labour’s internal pollster has an observation here, which is intriguing given the methodological insight revealed for the internal polling. Of course, as these data are not in the public domain, any conclusions drawn are not definitive. Finally, Eric Kaufmann (one n removed from a relation with our own SEK) has this intriguing take here at the LSE blog. I have one potential minor critique of the Kaufmann piece — his methodology is based on 130 of the Lord Ashcroft constituency level polls, and some of these were ancient in political terms. Speaking for the two constituencies that represent 15 of Plymouth’s 20 electoral wards, Plymouth Sutton & Devonport was polled in August, while Plymouth Moor View was polled in December. (The third, Southwest Devon, wasn’t touched, as it’s a very safe Conservative seat.) These polls estimated a 13 and 11 point Labour victory respectively; on May 7th, the Conservatives won both constituencies by 1.1% and 2.4%.
It is likely that no single cause will explain the polling failure of 2015. I have an additional theory that I’ll discuss soon assuming it passes prima facie.
(*) The other reasons include being elevated to an administrative role in my department (cue up Bunk to McNulty here), and that this election has increased my media calls significantly. I’ve done somewhere north of 60 appearances in the past twelve months. Rob suggested last week that I link these to LGM. I will in the future when I can, if only that you, too, can laugh along with the audience at home.
