Scottish referendum post-mortem

As I write there is still one council to declare, but the maths mean that the overall result is going to be Yes 45%, No 55%. So, how did the polls do?

The final pre-election polls had all tightly converged around the same figures - Yes 48%, No 52%, with every company was within one point of this. In fact the level of No support was three points higher than this. For a single poll a three point error would be within the margin of error, but every poll being off in the same direction suggests some systemic error.

A possibility is the shy noes/enthusiastic yesses we discussed before the referendum, but on the face of it a simpler explanation is just late swing. The YouGov recontact survey on the day, going back to the same people they interviewed in their final survey found enough movement between final survey to actually voting to take the figures to YES 46%, NO 54%, one point from the actual result and enough to explain the apparent divergence. From that it looks as though no was going to win anyway, but there was a further movement from yes to no when people actually got to the polling station.