What is an Exit Poll and how does it work?
How does the Ipsos Exit Poll work? Mike Clemence reveals how the data behind the Ipsos Exit Poll, provided to BBC, ITV and Sky to reveal at 10pm on General Election Night, is gathered and calculated to determine the likely result of the election
Ipsos has conducted an exit poll at every UK General Election since 1997. At the 2024 UK General Election, Ipsos is partnering with BBC News, ITV News and Sky News to deliver the official exit poll, with the results announced live at the close of polling at 10pm on the 4th July.
An exit poll is a very different type of poll compared with the prediction polling many polling companies publish in the run-up to an election. The method is based on intercepting electors as they leave their polling station and asking them to complete a mock ballot paper. By positioning teams at more than 130 polling stations across Great Britain, a detailed and high-quality picture of voting trends is collected that can inform a highly accurate seat projection.
Analysis is conducted by a team of senior academics working on behalf of the three broadcasters and led by Sir John Curtice. They use the data collected by Ipsos to inform the statistical modelling that is used to project the final result of the election. Further detail on the analytical process can be found through the links at the foot of this article.
Exit polling has a deserved reputation for accuracy, delivering results close to the final seat count in recent election campaigns. There are three key reasons for this:
- Exit polls deal with behaviour, not intention: By targeting electors immediately after they have voted, the poll gathers voting behaviour, rather than voters’ stated intentions ahead of the day. This also differentiates the exit poll from multi-level regression and post stratification (MRP) models which, although they provide a seat estimate, still rely on voting intention data.
- A simple methodology which minimises refusals: The UK exit poll asks one question only: “Who did you just vote for?”. It asks no further questions on background or motivation, which is more common in other exit polling worldwide. 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.
- Historical, local level data: Many of the locations used in the exit poll have been part of the poll for several elections. This means that there is a large archive of data on how the area voted in past elections, which allows for more nuanced analysis of voter swing at the current election.
Of course, no polling method is infallible and there are new dynamics at the current election which will test the analytical and fieldwork capabilities of the exit poll. But it is likely that the exit poll will provide a clear answer on who has won the 2024 election at one minute past ten on Thursday 4 July.
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