Exit ballot – how election prediction is calculated and strict rule about its use

Millions of Brits will cast their ballots on July 4 to determine the UK’s next government, but before the result is officially announced, the exit poll will give an insight into how the nation has voted.

After weeks of campaigning, either Labour’s Keir Starmer or Conservative Rishi Sunak will meet with King Charles III to ask permission to form a new government on Friday. Questions will no doubt be asked on the losing side about how they can better appeal to the British public, while the victors will quickly need to learn the intricacies of government.

But the nation will be given a rough idea of who the winner will be thanks to the exit poll. Unlike prediction polling run by various companies in the run-up to the election, an exit poll aims to accurately reflect how Brits actually voted.

The exit poll is published shortly after 10pm on election day. It is only published after polls have closed as strict reporting laws will be in place until then – as it could be seen as an attempt to influence the outcome.

Here is all you need to know about exit polls and how accurate they are.

What is an exit poll?

An exit poll is a survey that aims to give an accurate reflection of how the nation voted when polls close across the country at 10pm. Unlike other polls, electors who have left polling stations are asked to fill out a mock ballot paper, and the results are collected from across the country.

The exit poll is also unique in that it does not ask any follow-up questions, simply who the voter cast their ballot for. Teams stationed at scores of polling stations across the country then aim to get a detailed picture about the electorate and how it voted in particular areas.

According to IPSOS, which has conducted an exit poll at every UK General Election since 1997, its simple approach leads to a high number of willing participants. “As a result – and because it is administered face-to-face – relatively few refuse to participate: four in every five people approached at the 2019 General Election agreed to complete the mock ballot paper,” it said.

How accurate is the exit poll?

The current exit poll model is the brainchild of Professor John Curtice and statistician David Firth, who introduced it in 2005. The exit poll has since proven to be reliable with the exception of 2015 when a hung Parliament was suggested.

Instead, then-PM David Cameron snuck back into 10 Downing Street with a slim majority. But it has proven to be incredibly reliable in other instances, such as when it correctly predicted the number of Conservative seats in 2010.

Can the exit poll get the election result wrong?

While the exit poll has been proven to be relatively accurate, it is not infallible. New trends and dynamics could influence an exit poll and it could find itself having a different result.

But it would be unusual if the exit poll proves to be completely inaccurate. There is only one way to find out though, and that will be waiting until around 10pm on Thursday night.