That's right, as a Head of Community maths for a whole metropolitan area, tasked with breaking into hard to reach areas, I only have anecdotal evidence.
None of it, at all, comes from in depth studies from the DWP, Dept of Ed, IFL, B'ham Uni and the local authority. Nope, none, just my experience of working in mosques, temples, Gurdwara's, community outreach centres and colleges and of course, it's totally random that I visit these places, as no studies, of course, have been done, ever.