How does the General Election Exit Poll work?

When is the poll released? Where does it come from? How accurate might it be? All your questions answered...

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Who will win the 2017 General election? While we should know the final result around 3am, the exit poll will be the first clue to how the night will unfold. But what exactly is it? When does it come out? And, most importantly, how accurate is it? Here’s everything you need to know…

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What is the exit poll?

An exit poll is a survey of thousands of people leaving polling stations, asking how they voted. This differs from opinion polls, which ask people how they’re going to vote. This means the exit poll is more accurate as it’s not shaped by people who change their minds on the day itself.

How is the poll formulated?

From a top-secret location in London, academics analyse the exit poll results collected from over 100 selected polling stations. The samples are compared with surveys at the same places in the previous elections to calculate more accurate predictions.

Then comes the final stage: these predictions at a local level are then projected upwards to formulate that all-important national picture. 

Everything you need to know about the 2017 General Election night coverage

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How many seats does a party need to win?

326 is the magic number. If a party wins that many seats then they’ll have a majority in the Commons. However, if no party achieves this then the result is a hung parliament in which a minority party could form a government or a coalition could be formed. 

Who runs the exit poll?

BBC, ITV and Sky are sponsoring the poll, which will also be conducted by MORI and NOP. Head of the British Polling Council Professor John Curtice heads the closed-door analysis. 

When is it released?

10pm, 8 June on BBC1, ITV and Sky News. That’s the earliest time the poll can go out: Section 66 of the Representation of the People Act 1983 prohibits the publication, before the close of the poll, of any forecast, survey or estimate of how people have voted.

How accurate is it?

Very: since 2001 the exit polls have never missed a party’s seat count by more than 20.

Although the exit poll of 2015 wasn’t as accurate as it had been in 2010 or 2005, it did correctly forecast David Cameron would be on course to remain prime minister with a majority conservative party.

The 2015 poll predicted Con 316, Lab 239, SNP 58, LD 10, others 27. The actual result of the election was Con 331, Lab 232, SNP 56, LD 8, others 23.

It was a poll that many were sceptical about when first released. With former Liberal Democrat leader Lord Ashdown saying “If this exit poll is right, I will publicly eat my hat on your programme”. 

And much to the disappointment of viewers, he didn’t…

Exit polls have also correctly predicted over majority surprises. In 1997 it correctly predicted that Tony Blair would win by a landslide.

But it’s not always been so accurate. In 1992, the poll said the country was heading for a hung parliament with John Major’s Conservative Party predicted to “just get more seats than Labour”. However, the actual result showed the Tories got 65 more seats than Labour. 

Plus, in October 1974, the BBC predicted a 132 majority for Harold Wilson’s Labour party. The actual result was a three seat majority. 

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In other words, you best get the coffee ready: you’re going to have to stay up late to be sure which party’s won.