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Are election polls accurate?

In the run-up to the General Election, we're answering questions commonly searched for about the election, and asked on Twitter tagging @speakerpolitics. Tweet us now to ask your question.


There are plenty of polls out there trying to say what will happen in the upcoming general election - but are they actually accurate?

The accuracy and usefulness of polls seem to be a question that is raised nearly every time there is an election.

Pollsters such as YouGov and Ipsos MORI are producing voting intention polls, based on research of the opinions of the UK electorate. Pollsters will often interview a sample of people asking them who they intend to vote for, They will then use a model or set of methodologies in order to try and project the outcome of the election based on the current opinions of the electorate.

In recent elections, polls have often been inaccurate and results have proved much closer than actually predicted.


Why do polls differ so much?

Pollsters often use different methodologies and models to each other, which has recently led to quite significant differences in poll results. For instance, at the start of November, a YouGov poll gave the Conservatives a 14-point lead over Labour. However, in a poll from the same day conducted by ICM, the result was just a 7-point lead.

With random sampling, results will always vary from poll to poll, however, such significant discrepancies can seem confusing. 

Pollsters have to make decisions about what they expect the turnout to be at the election and how they treat undecided voters in their polls, so differences in results are definitely not unusual though.

Websites like Britain Elects show polls from multiple different pollsters. 


How much can polls change?

Polls could in theory change quite significantly. With 15 days left until the UK heads to the polls, nothing is guaranteed, despite what polls may suggest. In 2017, the Conservatives poll ratings dropped after the so-called 'Dementia Tax' was revealed in their manifesto. Key events and policy announcements have the potential to change polls quickly in any election.

This election could prove particularly difficult to predict, especially with the issue of Brexit.


What about Exit Polls?

An exit poll is released at 10pm once polling stations close on election day. An exit poll will show a projected result based on research on election day.

In recent years, the exit polls have been very accurate so the likely final result of the election can usually be judged long before all votes have been counted and confirmed. Again though, exit polls like any polls aren't necessarily accurate - factors may influence this such as if people are untruthful when taking part in research for the polls.


Overall, Yes or No to Polls?

Overall, the election polls are usually useful to an extent, generally predicting results correct within a few percentage points. While polls are generally correct, don't take them for granted, and also don't use them as a basis for deciding who to vote for - if you are not sure who to vote for, you can find out what each party is pledging at to help you make an informed decision.