This is probably OT, but I'm curious: why there are so many mathematicians here? It seems to me that the overall community is made by people who study/research math. Even undergrads post questions. Given that (at least in my country), math workers are a tiny fraction of the (academic) population, this seems an exception.
Mathematics is certainly disproportionately represented here, although it's only a minority of the site.
One reason is MathOverflow, which is arguably the most successful stackexchange site devoted to research-level academics. As a consequence, the stackexchange network probably has more visibility within mathematics than in any other academic field except computer science itself. When non-technical questions come up on MathOverflow, people are often advised to come here instead, so we get a steady stream of visitors interested in mathematics.
A second reason is critical mass. If a mathematics student or professor visits this site, they will quickly see that it's a welcoming and useful place to ask/answer questions, while this may be less apparent in some other fields. The net result is that first-time users in mathematics are probably more likely to become active participants.