by Mish
A recent poll by Survation shows Labour within one point of winning the election. Is a Labour win possible?
The Independent reports Conservative lead over Labour cut to just one point, new poll finds.
The problem with placing a lot of stock in that headline is it’s just one poll. Let’s look at all the recent polls as depicted by Wikepedia.
Not a single poll ever has put Labour in the lead for the 2017 election.
I give more weight to the most recent polls. The average lead for the Conservatives for polls that finished June 2 or later (above the dashed line) is 6.4.
With Brexit, three of the final six polls had Leave winning. Here is my final poll snapshot from my blog.
Brexit Polls Final Tally
UK Polls Skewed
Nate Silver (anyone remember him?) asks Are The U.K. Polls Skewed?
In April, when U.K. Prime Minister Theresa May called for a “snap” general election for June 8, polls showed her Conservatives with an average lead of 17 percentage points over Labour.1 Such a margin would translate to a giant majority for Conservatives: perhaps as many as 400 of the 650 seats in Parliament. (Conservatives currently control 330 seats; 326 are needed for a majority.) After several unpredictable years in U.K. politics — marked by Conservatives unexpectedly winning a majority in the 2015 general election, the successful Brexit referendum, and David Cameron’s decision to resign as prime minister and Conservative leader — such a result promised to provide May with a mandate as she negotiated the terms of the U.K.’s exit from the EU.
Instead, polls suggest that the Conservative majority is under threat. As we remarked back in April, May’s move was riskier than it seemed because polls in the U.K. have been both highly volatile (shifting abruptly over the course of election campaigns) and fairly inaccurate (often missing the mark on Election Day itself). Conservatives’ lead was wide enough in April that they probably needed multiple things to go wrong to lose their majority. But if there were both a shift toward Labour during the campaign and a pro-Labour polling error on Election Day, it could be at risk.
The first part of May’s nightmare scenario has come to fruition. Recent surveys show Labour zooming up in the polls and Conservatives having declined somewhat (although some of Labour’s gains have also come at the expense of Liberal Democrats and other parties).
The timing of the shift partly coincides with the release of the Conservative party manifesto two weeks ago, which included a proposed change to health care spending that opponents soon labeled as a “dementia tax.” (None of the polls yet reflect any potential effects from an incident on Saturday night at London Bridge, when a van reportedly hit a number of pedestrians.)
May’s Conservatives are now only a normal-sized polling error away from a hung parliament. On average in the U.K., the final polling average has missed the actual Conservative-Labour margin by about 4 percentage points. (This is twice the average error in U.S. presidential elections.) If Labour outperforms its polls by that margin, Conservatives would win the popular vote by only about 3 points — and May would probably have to find a coalition partner to form the next government. If the polls were to miss by any more than that in Labour’s favor, a variety of yet-more-unpleasant scenarios could crop up for May, including some where Labour leader Jeremy Corbyn tried to form a government instead.
But there’s a catch — and a potential saving grace for May. Although the polls haven’t been very accurate in the U.K., the errors have usually run in the same direction: Conservatives tend to beat their polls there. (There’s been no comparable phenomenon in the U.S., where polls have erred toward both Democrats and Republicans about equally often in past elections.)
If that’s the good news for May, here’s the bad news: The conventional wisdom is still pretty confident that she’ll win a majority, more so than the polls are. And the conventional wisdom is almost always wrong.
I’m not just being a trollish contrarian here. The conventional wisdom, at least as espoused by (i) betting markets and (ii) mainstream media coverage, has a remarkably poor track record in major elections around the world in recent years. In the U.K. last year, pundits and punters were irrationally confident of a “Remain” victory in the Brexit vote, even though polls showed it only barely ahead of “Leave.” In the U.S., they ignored how much the race had tightened in the final weeks of the campaign and data that showed Trump would likely do better in the Electoral College than the popular vote. In the French presidential election last month, the conventional wisdom was irrationally worried about a Marine Le Pen victory even though she trailed Emmanuel Macron by 20 to 25 percentage points. In fact, it was Macron who beat his polls, winning by 32 points.
These experiences have given rise to what I’ve called the First Rule of Polling Errors, which is that polls almost always miss in the opposite direction of what pundits expect:
Silver’s article is very lengthy. It’s also a good read, especially after some disastrous predictions about Trump’s chances of winning. In this case, he is not quite so confident.
Silver concludes: “Given the poor historical accuracy of U.K. polls, in fact, the true margin of error7 on the Labour-Conservative margin is plus or minus 10 points. That would imply that anything from a 17-point Conservative win to a 3-point Labour win is possible. And even an average polling error would make the difference between May expanding her majority and losing it.”
For now, I will stick with a 6-8 point win for the Tories. The primary risk is the pollsters changed their models because they blew the last election and are now too far skewed the opposite direction (in favor of the Tories).
If the next set of polls after the recent London Bridge attach change dramatically, I will reassess.
Mike “Mish” Shedlock
