LONDON (Reuters) - British pollster YouGov will publish a poll showing how people have voted in the European Union referendum shortly after polling stations close on Thursday, hoping to repeat its successful prediction of the 2014 Scottish independence vote.
As in 2014 and unlike in national elections, British broadcasters on Thursday will not conduct exit polls - in which people are asked as they leave polling stations how they voted - because the margin of error for an event which has little precedent is too large.
YouGov’s poll will be based on responses from a pre-selected group of people seen as representative of the wider electorate on how they actually voted in the referendum.
Its findings are due to be announced by Sky News soon after polling stations close at 10 p.m. (2100 GMT).
In the absence of exit polls, the YouGov survey will be closely watched by the 24-hour foreign exchange market GBP=, which has see-sawed in recent weeks as polls have shown shifts in support for the rival "In" and "Out" camps.
The online survey will be drawn from a panel of people who have previously been polled by YouGov about their voting intentions and who have agreed to share their decision once they have voted, a spokesman for YouGov said.
The figures will be weighted for a number of factors, he added, declining to comment further on specifics. No figure for the number of people to be surveyed was immediately available.
A 2014 YouGov poll released as Scottish polling stations closed came very close to accurately predicting the result of Scotland’s independence referendum.
That poll showed the campaign against independence winning with 54 percent of the vote. The official result gave the anti-independence campaign 55.3 percent of the vote.
YouGov and other major pollsters failed to predict the outcome of Britain’s 2015 parliamentary election. Prime Minister David Cameron’s Conservatives won it with a comfortable, albeit slim, majority, despite months of opinion polls showing them and the main opposition Labour Party running neck-and-neck.
The event was labelled a “fiasco” for pollsters and was followed by an inquiry by the British Polling Council. Only one exit poll was close to being right.
The most recent YouGov poll, for the Times newspaper on Monday, showed 44 percent of Britons would vote to leave the EU and 42 percent would vote to remain. Some other recent polls have shown the “In” campaign narrowly ahead.
Another polling firm, TNS, will also release information at 2100 GMT on Thursday on the reasons for any last-minute changes of heart among voters. Two hundred people surveyed for voting intentions in the days before the referendum will submit details of how they voted and explain any changes of mind.
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Reporting by Freya Berry; editing by William Schomberg and Gareth Jones