Let's return briefly to the false claim that was made the other day that public opinion on independence hasn't budged for years. It's probably best to demonstrate in precise terms why that isn't true, before any myth is allowed to take root. I've calculated yearly averages for all independence polls in 2018, 2019, and 2020 to date. As you can see, there has been a clear increase in the Yes vote year on year.
Should Scotland be an independent country?
The only polls I've excluded are the notorious Scotland in Union propaganda polls that were sometimes portrayed in the media as "independence polls", but in fact were nothing of the sort, because independence wasn't even mentioned in the question. On the other hand, I've included the YouGov / Hanbury poll from earlier this year, which used a non-standard question but with neutral wording. (If that poll is excluded, the Yes vote for 2020 is even higher.)
So if there has been a gradual increase for Yes, why is it possible to dredge up headlines from past years about Yes being in the lead? Basically there were a couple of previous purple patches where Yes appeared to be ahead - one was just after the 2014 indyref, when the positivity of the campaign was still fresh in people's minds and when David Cameron appeared set to betray The Vow. The second was just after the EU referendum, but it didn't last long at all. There was then a prolonged slump in 2017 and 2018 when both YouGov and Panelbase were consistently showing Yes hovering somewhere between 43% and 45%. Self-evidently, the situation has improved markedly since those days.
Outside of the two previous purple patches, there has also been the odd individual poll from Ipsos-Mori showing a Yes lead out of the blue. It's probably no coincidence that Ipsos-Mori are the only firm that don't weight by past vote - although whether that makes them more accurate or less accurate is open for debate.