I am pure mathematician, and my impression (which I'm sure is not unique) from frequenting this site for some time is Academia.SE there seem to be a relatively large number of mathematicians on this site, as compared people from many other disciplines, especially social sciences. I suspect this is in large part due to a strong mathematical involvement with SE beginning with MathOverflow and to some extent with MathStackExchange.
Question: Do we have/can we get any rough estimates of a make-up community by field?
The idea behind this question is to get a more concrete sense of things like how much field-dependent bias there is to various posts on this site, as well as which communities we are serving well and which we are not.
A couple of simple ideas are: parse user profiles/SE network usage and/or look at what discipline tags people use. (As of now, the top 3 discipline tags by posts are: math (1494), CS (1064), physics (296).) Perhaps restrict to a weak notion of regular users such as has visited at least once/month for at least 3 out of the last 6 months.