[kibwen]

It might also be partly explained by selection bias among SO's audience. At my first real job there was no other developer there below 40, and a few approaching retirement age (indeed, I was brought on to replace a developer who had retired). But I was the only one who used SO, and really the only one who turned to the internet for answers at all rather than reaching for the books on their shelves.

(And also, our proportion of female developers was way, way higher than 5%.)

Older developers are certainly out there, but they're woefully underrepresented in open source.