Polling is an inexact science.
Not only does ‘random’ sampling offer some challenges but models try to predict which type of voters will turn out. In a general election there is lots of historical data to draw upon but a referendum is a unique event.
One pollster is sounding alarm bells. Martin Boon, director of ICM, told BBC Radio 4:
‘This referendum has the potential to be a polling Waterloo, the biggest since 1992 when the polls got it wrong.
‘I think and hope that the best that we in the industry can hope for is that we dodge a bullet, but it’s entirely possible the bullets do start spraying our way.
‘We are dependent on a pot of people which is defined, but we don’t know how big it is and in my view it won’t be big enough.”
Factors that could skew the vote to the Yes (independence) side:
- Strong Yes support may come from people who don’t normally vote, like young voters
- Young men are less likely to answer phone surveys or speak to canvassers, so they might be underrepresented
- Land-line phone polling my miss young people
Why the No vote might be underestimated:
- People may feel pressure to say they’re voting for independence in polls
- No voters may say they’re undecided rather than appear unpatriotic towards Scotland
