Is the exit poll accurate? How close prediction comes to actual election results

A member of staff counts ballots at the main Glasgow counting centre in Emirates Arena in Glasgow, Scotland, on June 8, 2017, after the polls closed in Britain's general election.
Prime Minister Theresa May is poised to win Britain's snap election but lose her parliamentary majority, a shock exit poll suggested June 8, in what would be a major blow for her leadership as Brexit talks loom. / AFP PHOTO / Andy Buchanan        (Photo credit should read ANDY BUCHANAN/AFP via Getty Images)
-Credit: (Image: ANDY BUCHANAN/AFP via Getty Images)

When the clock strikes 10pm on election day, polling stations will close and the exit poll will shortly be released.

The exit poll give a snapshot of how millions of people voted in the actual election. The polling, which is conducted at 144 stations across the country, asks people to fill out a replica ballot of how they voted.

Here's what you need to know about the polls - and their accuracy.

How accurate are exit polls?

The exit poll's accuracy appears to have gotten better with time. The first British exit poll was in 1974, wherein a Labour majority of 132 was predicted, though the actual majority was three.

More recently in the past few elections, the poll has produced a very accurate projection of the official result.

Polling expert Sir John Curtice, a professor of politics at Strathclyde University in Glasgow, said: "It’s tended to be relatively accurate, it’s not perfectly accurate, but there’s been a number of occasions in which it has ended up proving rather more accurate than what the opinion polls have been.

"Not that I’m suggesting that’s necessarily going to be the case this time but, on occasions like 2015 and 2017, the exit polls proved to give a better guide."

What did the exit polls say in the last few general elections?

In the last election in 2019, the exit poll predicted a Conservative majority of 86 seats. The final margin was an 80-seat majority.

Preceding this, the 2017 election exit poll correctly predicted the Conservatives would be the largest party, but did not predict there would be a hung Parliament.

The 2015 exit poll proved more accurate than opinion polls, but did not predict a Conservative majority.

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