Was very different to Tesco earlier in the week, which I guess was around 50% - it seemed a bit less than usual ~60% levels, but could also have been random variation / sample bias.
I'm fairly sure levels were higher a year ago and have gradually declined, but I can't remember too clearly and wouldn't stake anything important on that.
One correlation might be people in groups being even less likely (compared to individuals/couples), but I guess that's self-selective given the request not to do that in the first place.