Odds of a Scottish Yes vote are fading fast

August 20

A  pro-independence supporter wearing a kilt and holding the Scottish flag joins people gathered for a rally in Edinburgh on Sept. 21, 2013. With a month to go until Scotland votes on independence from Britain on Sept. 18, 2014, polls suggest the plan will be defeated, leaving First Minister Alex Salmond and the Yes camp in an uphill battle to secure victory. (Andy Buchanan/AFP/Getty Images)

The following is a guest post from social scientist Arkadiusz Wiśniowski of the University of Southampton.

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Time is ticking away fast in campaigning for the referendum on Scottish independence. Interest in the referendum reached new heights on Aug. 5 with the televised debate between Alex Salmond, first minister of Scotland and leader of the Yes campaign, and Alistair Darling, chairman of the Better Together campaign. Surprising expectations, Salmond was widely agreed to have stumbled in the debate on the question of the new Scotland’s currency. This was reflected in snap polls that followed the TV debate, with Darling viewed as the clear winner. The verdict of the Scottish public was also reflected in subsequent polling on voting intentions for the referendum, which observed a clear swing toward the No campaign. When the most recent polls are included in our forecasting model (detailed in this post), they produce a similar swing in the predicted share of votes on referendum day.

In the figure below the blue line indicates the time trend in the percentage of responses favoring independence (excluding undecided and those not voting) in the polls. The probability distribution, shown in red on the right-hand side of the figure, indicates the predicted share of votes for Scottish independence on referendum day. Our forecast suggests the odds of a Yes vote for independence are fading fast. The forecast is now centered at 47 percent with the 95 percent predictive interval ranging from 44 percent to 51 percent. This differs substantially from our forecast approximately three weeks ago, reflecting this sharp movement in the polls. The probability that Yes campaign will obtain more than 50 percent of the vote is now only just above 5 percent.

Predicted shares of the vote in Scotland for independence from the UK. credit: Arkadiusz Wiśniowski
Predicted shares of the vote in Scotland for independence from the UK. credit: Arkadiusz Wiśniowski

With five more weeks of the campaign to go, and another TV debate on Aug. 25, there is still scope for more late movements in public opinion. However, our latest forecast suggests that the pro-independence campaign is fighting an uphill battle.

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