Old enough to know that this has been asked before:
https://news.ycombinator.com/item?id=2322031
https://news.ycombinator.com/item?id=517039
https://news.ycombinator.com/item?id=126923
I think it's OK to ask this question after 2 years. It's great to see how communities change over the years.
Yes, I know it's not scientific at all and does a poor job of reflecting real demographics. But, if you think there's value in asking, then there's value in comparing previous answers.
Went from a couple hundred answers in 2008-2011 to +3000 today, and counting.
The distribution doesn't seem to have changed much other than the current fool answers, hard to tell since the charts are not in absolute scale. Would be cool to aggregate all the years for comparison, but I have no idea how to merge the age ranges.
Script used to get the data: https://gist.github.com/ricardobeat/5370218