I happened to be chatting with an Earth Science prof this morning. He mentioned that enrolment in Earth Science graduate degrees was strongly counter-cyclical (with a short lag). When the job market weakened, more students decided to get a graduate degree. When the job market strengthened, applications for graduate programs dropped.
There seems to be nothing surprising about that. This is ECON 1000 stuff. The main cost of getting a degree is the opportunity cost of lost wages. When you can't get a job, the opportunity cost of getting a degree is low, so more people invest in human capital. And there's presumably nothing special about Earth Science; it's just that mining and exploration fluctuate a lot, so it's easier to see this effect in Earth Science than in other subjects.
But it's very surprising when you compare it to other forms of investment. Business investment is strongly pro-cyclical.
Both human and non-human capital are used to produce goods. Why should investment in human capital be counter-cyclical, and investment in non-human capital be pro-cyclical?
I think there's a simple answer, and that answer tells us something about the nature of the business cycle.