How accurate is the exit poll, what is it and are they ever wrong?

Rebecca Speare-Cole12 December 2019
WEST END FINAL

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A general election exit poll has predicted a landslide victory of Boris Johnson's Conservatives.

The forecast put the Tories on 368, Labour on 191 and the Lib Dems on 13 after the polls closed at 10pm.

The SNP is predicted to win a massive 55 seats in Scotland while the Brexit Party will win no seats at all.

If that proves to be correct, Mr Johnson will have the majority he needs to push through his Brexit plans.

But how do exit polls work and how accurate have they been in past elections?

Throughout the day, the exit pollsters built up a picture of how the country was voting.

They ask the nth voter to stop and fill out a replica ballot to indicate how they just voted.

Volunteers begin to count ballot papers during the general election count at Mill Bank leisure centre in Hartlepool
Getty Images

As the method advanced since the first exit poll in 1974, the forecasts have become more and more reliable.

The 2005 and 2010 exit polls were both spot on in terms of the majority seats won, earning the poll a reputation for accuracy.

In the first, it estimated that Tony Blair would win a majority of 66 while the second predicted that David Cameron would be 19 seats short of a majority.

In 2017, despite it underestimating the number of Conservative seats by four, the poll correctly predicted that the party would lose their majority and would need to be propped up the DUP.

However, in 2015, the poll wrongly predicted a hung parliament, suggesting Mr Cameron would be 10 seats short of a majority.

The then-Prime Minister actually won four seats more than needed for a majority so that he could govern without the support of the Liberal Democrats.

The exit poll is therefore not a foregone conclusion and the nation will have to wait until the results flood in.

But if it predicts a Conservative majority of 30 or more, the final result is very unlikely to be a hung parliament.

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