Those Scottish independence polls: why the Don’t Knows mean Yes should be concerned

by Stephen Tall on September 10, 2014

Since the YouGov poll showing a narrow Yes lead was published at the weekend the Westminster Village has flailed into hyper-active over-drive. Even today’s Prime Minister’s Questions was cancelled to allow the three party leaders to descend on Scotland and bolster the flagging No campaign.

Personally I cannot begin to describe the extent of my ambivalence. As a federalist, I’m caught in a pincer of equal distaste for Alex Salmond’s and his cybernats’ nationalist aggression and the shrill Anglo-presumption of unionist politicians and commentators that the Scots need saving from themselves.

The Better Together campaign’s frayed nerves will be partially soothed by the latest poll released tonight purporting to show No leading by 53%-47%. I use the word purporting quite deliberately. Here’s why, courtesy ComRes’s blog:

Ignore the “don’t knows” at your peril

Most of the recent headlines have been generated by reports which have excluded “don’t know” respondents from the calculation. This gives a neat prediction of the final split. But it can be a misrepresentation of the polls.

An analogy: if we asked 1000 people whether they prefer Coca-Cola or Pepsi, and 400 preferred Coca-Cola, 350 preferred Pepsi, and 150 had no strong opinion or were undecided, it would then be wilfully misleading to say that 53% of them prefer Coke. This is effectively the analysis that many journalists (and some pollsters) have been making.

The truth is that while the two headline-grabbing, market-bashing polls of the week are each showing the same trend (an upward tick in “Yes” support), they are otherwise showing two very distinct pictures:

Pollwatch image - comres

The question is whether TNS-BMRB’s “don’t knows” will split evenly into “Yes” and “No”, or whether they are more likely to break towards one side. The evidence from previous referendums worldwide is that most “Don’t know” respondents will end up backing the “status quo” option on voting day. If that is the case, then “Yes” should be very concerned about their 39% figure this close to the vote.

Some will argue that there no longer is a status quo option on the ballot – that we are now into Devo Max vs. Full Independence territory. But the former clearly involves less change and less of the unknown, and we should still expect cautious and undecided voters to lean this way on voting day.

Keep your eye on the “don’t knows”.

Yes. And another thing to keep your eye on is the polling trends. You can see all the polls published to date at UK Polling Report here. Perhaps we’ll be blind-sided by a late surge, but it’s going to take more than one poll well within the margin of error to convince me Yes Scotland have a hope of winning outright.

* Stephen Tall is Co-Editor of Liberal Democrat Voice, and editor of the 2013 publication, The Coalition and Beyond: Liberal Reforms for the Decade Ahead. He is also a Research Associate for the liberal think-tank CentreForum and writes at his own site, The Collected Stephen Tall.