The underlying rates of degrees from the various fields haven't changed all that much. Finding a few humanities students who can't find jobs isn't all that helpful.

http://nces.ed.gov/programs/digest/d13/tables/dt13_318.20.as...

The main issues are that, since the 70s, a handful of things have happened that students (as a massive whole) haven't reacted appropriately to:

1) There are simply fewer job openings in many of these fields than there once were. http://www.bls.gov/news.release/empsit.t17.htm (you'll have to step back through these reports over time, but note that the increasing industries tend to be the lowest wage industries)

2) The massive rise in the cost of education, coupled with the fact that almost any of the few good-paying jobs requires a bachelor's degree or higher. Supply of workers > demand for workers depresses wages. https://trends.collegeboard.org/college-pricing/figures-tabl...

3) Private sector jobs in a good many fields have been outsourced, with low wage service jobs on the increase. http://online.wsj.com/news/interactive/MULTINATL0419

4) Public sector jobs have become increasingly rarer. http://www.lasvegassun.com/news/2011/sep/16/census-shows-big...

5) Home prices have dramatically increased over this period (which may actually be a good thing, since the workforce is now more mobile than ever before) http://www.economist.com/blogs/graphicdetail/2014/02/us-hous...

6) Unions, for all their problems real and perceived, were once actually pretty good at holding the line on wages, but have seen ever-decreasing membership. http://www.bls.gov/news.release/union2.nr0.htm

7) An increasing portion of the workforce is contingent (temporary and/or seasonal). http://www.dol.gov/_sec/media/reports/dunlop/section5.htm

Does any of this mean they didn't pick the "right" degree? Maybe part of the problem can be found here. However, the problem is so large among millennials, I'm not sure choice of degree accounts for all that much of why recent college grads have boomeranged. My point is that while students with degrees in various fields hasn't changed much, the rest of the world around them has changed quite a bit. Most of it can't simply be solved with a different degree or more passion.