In a couple of recent blog posts (here and here) at the Marginal Revolution, friend of Cyclingprof Alex Tabarrok laments that college students are not enrolling in fields of study with the greatest economic potential. The graph below shows that enrollments in math, science, and engineering have stagnated since the 1980s, while students prefer fields with lower pay (and presumably generate lower economic returns to society). A recent Georgetown University study (here) indicates that engineering grads earn the highest (median lifetime) salaries ($75,000), while psychology and social work grads earn the least ($42,000).
It's worth remembering, however, that universities are not only vocational institutions. They, in part, places for students to follow their bliss, even if their bliss is economically shortsighted. Some reports (see, e.g., here) suggest that, while liberal arts majors start off in the job market at a comparative disadvantage to science and engineering majors, they catch up fairly quickly once they are on a career trajectory. Most importantly, the economic returns to any college degree remain much higher than for a high school diploma (let alone for high school drop-outs).