This is a quick update to yesterday’s post on polling for the referendum on the independence of Scotland from the UK. The final result is 55.3% for No (i.e. staying in the union), 44.7% for Yes. This is consistent with the opinion polls, which predicted a win for No, but the margin is certainly bigger than predicted by the opinion polls, especially in the run-up to the referendum.
The image below from whatscotlandthinks.org shows a “poll of polls” – a running mean of opinion polls – which is a smoothed version of the figure I showed yesterday. The average of the last 6 polls on the day before the referendum gave a prediction of 52% for Yes – only a 4 percentage point difference compared with the 11 point difference seen in the referendum. This vindicates Stephen Fisher’s analysis showing that opinion polls tend to overestimate the desire for constitutional change.
If you ignore the narrowing in the gap that apparently occurred in the last two weeks, the polls seemed to give a pretty good prediction from April to August. So perhaps this wasn’t a last minute surge for Yes, but a “patriotic spiral of silence” from No voters, as Martin Boon suggested. But I’ll leave that question to the psephologists.