Years ago when I got started down the road that led me to identify as a Skeptic and an Atheist, I heard a lot about how few blacks (in America) were atheists and skeptics, and how women were more religious than men. I know studies are still being done on these topics, and people are trying to get more involved, but I somehow doubt the answer is simply "have harassment policies, get rid of t-shirts, and invite any woman to speak, qualified or not". I'm not sure what the rest of the world is like, but I know the demographics are (perhaps slowly) changing here in the States. I also consider what studies have shown is that people tend to want to fit in and be around their own "kind" (shades of Ken Ham). People want to be comfortable, and I think, and may be completely wrong as I have no data, that as long as the first things we identify as are race or sex, people in general will not want to attend functions that are attended by the majority of what they do not identify as. Obviously some people can do that already.
The other thought I had is based on some of what I heard as reasons why people don't attend - they think that there is nothing for them, or topics that are not attractive to them. It's ok to hear a talk about vaccines from someone with no medical or even science background (although I'd prefer they have one of those), but how about a topic like - teaching skeptical thinking with no money - something we face in schools all the time.
I also have to wonder about the demographics - most of this seems to be focused on the big (TAM, Skepticon, etc) - what are the local groups like? Are they "havens for old white men" (not from what I hear), and they are where the real work gets done. Dog and pony shows are fine, but most things happen at the local level where (to use yet one more cliche) the rubber meets the road. I know there has been an effort mentioned by the A+theism crowd to brand any local group that thinks like they do in the basics (I'd say that's pretty much everyone, even if we disagree with other things) as A+ by default, so they can market their brand name.
In all the posts I've read, I have seen a lot of comments on "brand name" etc - all these marketing terms - one of the first things done, before they even published what they stood for, was to design a logo! Is there a large number of non-scientists, say, people who've studied communications or marketing, in this group, or is that just a function of our consumer culture?