By the early nineties I was organising some tours for people and had a fairly comprehensive filing system for contact details for the folk clubs available in the UK. At that time I knew of about 700 clubs, although perhaps a quarter either didn't book guests or only had one or two per year. What was very noticable was that when I started going to clubs in the '70's every university & college had its own club but by 1990 these were almost non existant. So based on that, and also on the fact that a lot of pub venues had also disappeared by 1990, my 'educated guess' of venues around mid '70s would be perhaps 2000