The exit poll: what is it and how does it work?

3 July 2024, 13:45

Here's what you need to know about the first major moment of election night, the exit poll, and what its result could mean ahead of the eventual outcome the general election.

As the clock strikes 10 on the night of July 4, the first big moment of election night ensues: the exit poll. But as people tune in to get the first clues of the election result, what does it actually mean and how is it calculated?

What is an exit poll?

An exit poll is an opinion poll that estimates the result of an election before all the votes are counted, by asking people how they voted.

Tens of thousands of people across the country will be asked to fill out a replica ballot as they leave their polling station. The result will be published shortly after 22:00 on election day, when polling stations close and voting ends.

How does the exit poll work?

The polling company Ipsos will carry out the exit poll for the General Election. It will place interviewers at around 144 polling stations across the country.

The stations are chosen to demographically represent the country, they include rural and urban seats and are slightly weighted to favour marginal areas.

To "maximise confidentiality of people's votes" identical ballots and a replica box are used for people to file their votes. The amount of people asked to contribute to the exit poll depends on the size of the registered electorate in each area.

The exit poll estimates the election results using the model devised by polling expert Professor John Curtice and statistician David Firth.Where possible, they visit the same polling stations at every election.

Professor John Curtice has said "the method of the exit poll is that you compare the results in the selected polling stations this time, with the results of the exit poll last time."

How accurate are exit polls?

The accuracy of exit polls seems to have improved over time. The most recent general election exit poll in 2019 predicted a Tory majority of 86 seats and the final result was a majority of 80.

In the previous election in 2017, the exit poll correctly forecast the Conservatives would be the largest part, but did not predict a hung Parliament.

Professor Curtice has said recent exit polls have been "relatively" but not "perfectly accurate", but often more accurate than opinion polls.

"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."