[figure8]

Seeing that 70% decline in number of developers (on SO) from age 30 to age 40 and assuming they are still working, what do the older "has-been" developers do now and what titles do they have? Perhaps they have never heard of SO? Or they have stopped needing and/or using SO? Statistics based on educational website usage seem to always skew younger.

Analogously, if I measured academic skills and availability by time spent in libraries and time spent teaching, I'm sure we'd see a similar peak in 20's because grad students spend so much time doing both these things and productive professors need this less.