HSBC: The 'Don't Knows' will keep the UK in the EU

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Britain is set to vote on whether to remain in the European Union on June 23.

The result of the UK's referendum on European Union membership might be decided by the basic human need for safety.

The large number of people answering "Don't Know" to polls on which way they'll vote in the June 23 referendum will swing the result towards staying in, according to HSBC.

Here's HSBC economist Liz Martins (emphasis ours):

Given a binary choice of Leave or Remain - matching, of course, the choice that will be shown on the ballot paper on the day - the balance tends to shift in favour of Remain.

Given that 10-20% of respondents in most online polls answer 'don't know', this is a significant portion of potential support that is not being counted.

HSBC also cites Stephan Shakespeare at polling company YouGov who said: "The deep human drive to avoid risk is likely to become increasingly powerful as we get closer to a real decision which cannot easily be changed once it is made."

Friday marks the official start of political campaigning on the EU referendum, which is 10 weeks away.

The polls show a slight lead for the Remain camp, but that the lead is narrowing:

HSBC

Whether the "Don't Knows" actually sway the referendum away from a Brexit in June is down to how likely they are to vote.

HSBC said that pollsters "found that in general elections in the UK, turnout among those who had previously declared themselves to be undecided was not markedly lower than those who had already made their minds up."

So the chances of a Brexit could be a little more remote than the polls suggest.