EU referendum: What the polls aren’t telling you

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Polling data is coming out thick and fast ahead of the UK’s historic referendum tomorrow.

While there have been moments in which Remain seems to have gained the upper hand, or Leave has undergone a surge, most polls suggest a dead heat, with the vote going to the wire.

In June so far there have been 25 polls, 11 of which were won by Remain, 13 won by Leave, with one tie.

However, much of the polling data showing a shift to Remain or Leave is missing one key factor: the undecideds.

In 20 of the 25 polls, the margin that either side “won” by was overshadowed by the “don’t knows”.

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Take the latest poll by Survation. It showed 45 per cent in favour of Remain, and 44 per cent in favour of Leave. That leaves 11 per cent who are undecided: if most of that 11 per cent falls on Leave, then they could win by a landslide.

Now, you can look at that same poll by “excluding undecideds”. That shows Leave has a lead of nearly two per cent.

But it would be insightful to look at what happens when the undecided voters are squeezed. This put Remain ahead by one per cent.

The latest YouGov poll gave Leave a two percentage point lead, placing it on 44 per cent to Remain’s 42 per cent. Nine per cent said they did not know how they would vote.

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Of those who did not know, 27 per cent per cent said they’d probably end up backing Remain, with 19 per cent saying they’d vote to leave.

Or take the last Opinium poll before the vote. It put both sides at 44 per cent, but with 10 per cent declaring themselves undecided.

When that 10 per cent were asked which way they were leaning, 36 per cent said Remain and 28 per cent said Leave.

So, the data suggests undecideds tend to back Remain.

Or as Matthew Shaddick, head of political odds at Ladbrokes, said: "Past experience, in particular in the Scottish Independence Referendum, has suggested that undecided voters tend to break for whichever side they perceive as the least risky option."

"Remain will be hoping that Project Fear does the job in the privacy of the polling booths tomorrow."