London, We Have A Problem: Why British Pollsters Were So Dreadfully, Terribly WrongPosted: May 13, 2015
Michael Barone writes: “The world may have a polling problem.” That’s the headline on a blogpost by Nate Silver, the wunderkind founder of the fivethirthyeight.com website. It was posted on 9:54 Eastern Time the night of May 7, as the counting in the British election was continuing in the small hours of May 8 UK Time.
“Polling provides useful information, but information whose reliability is often ephemeral and increasingly, it seems, limited.”
That was an hour after the result in the constituency of Nuneaton made it clear that all the pre-election polls were wrong. Nuneaton, in the Midlands just east of Birmingham, was number 28 on a list of 42 marginal two-party contests. Projections based on pre-election polls were that Labour would win 35 of these 42 seats. Instead Conservatives won 34 of them.
Nationally, the pre-election polls predicted that Conservatives would win about 280 seats, barely ahead of Labour and far short of a 326-seat majority. The exit poll pegged them at 316. They ended up winning 331.
“Readers may have noticed that all these errors seem to come from one ideological direction. In nations where the dominant media lean left–the New York Times and the old-line TV networks here, the BBC in Britain, Ha’aretz in Israel–opinion on the right has been understated in the polls.”
Something similar happened in 1992, when pre-election polls showed the two parties tied but Conservatives won by a 7.5-point margin. The most common explanation, advanced by Conservative analyst Rob Hayward: “shy Tories” were unwilling to tell pollsters they favored the Conservative party.
“Evidently, some people don’t want to identify themselves as troglodytes to telephone interviewers or even on robocalls.”
British pollsters made adjustments then but, as Hayward notes, they didn’t work this year. Internal party polls apparently did better. American pollster Stanley Greenberg, working for Labour and using a longer questionnaire, found the party’s numbers sagging. Australian consultant Lynton Crosby, running Conservatives’ campaign, assured party leaders they would win 300 seats.
Silver correctly points out that Britain isn’t the only country where recent polls have been off. Israeli polls projected that Benjamin Netanyahu‘s Likud party would win 22 seats in the Knesset. Instead it won 30 and Netanyahu formed a government.
And writing just after America’s November 2014 off-year elections, Silver concluded that polls tilted toward Democrats. Reviewing the data then, I noted that in seriously-contested statewide races Democrats tended to…(read more)