"I suspect you'd get the most RoI on education related to what the economy needed at the time. However if the market is compensating employees fairly* then students will likely pick what enjoy doing which also best fits the needs of the economy (as dictated by the benefits of the job)."

The problem being that much education has a minimum of 4 year lag time. So one could go into a degree program when the market is hot, only to see it cool off by the time they graduate.