[Callers] number of contra dancers?

[Duplicate posting to trad-dance-callers and SharedWeight lists] A friend recently wrote me, "I am trying to pin down an unpindownable number: namely the number of people in the world who regularly contradance. Any idea of this number, or anyone who might steer me to it?" I'm wondering if anyone on this list has tackled this question, has developed even a crude methodology, and would be willing to share what you came up with. As for "the world," with the exception of the folks in Denmark and in England, I think we're really talking about the US and Canada in terms of any significant numbers. I can ask friends ub Denmark for their estimates. The annual country dance festival in Prague brings together several hundred dance enthusiasts from central Europe, though their definition of "regular" is certainly different from someone in the Boston or SF Bay or DC areas. David Millstone