Once, being a college professor was a career. Today, it's a gig.
This doesn't actually mean that there are fewer full-time professors today than four-decades ago. College faculties have grown considerably over the years, and as the AAUP notes, the ranks of the tenured and tenure-track professoriate are up 26 percent since 1975. Part-time appointments, however, have exploded by 300 percent. The proportions vary depending on the kind of school you're talking about. At public four-year colleges, about 64 percent of teaching staff were full-time as of 2009. At private four-year schools, about 49 percent were, and at community colleges, only about 30 percent were. But the big story across academia is broadly the same: if it were a move, it'd be called "Rise of the Adjuncts."
That, broadly speaking, is the transformation captured in the graph below from a new report by the American Association of University Professors. Since 1975, tenure and tenure-track professors have gone from roughly 45 percent of all teaching staff to less than a quarter. Meanwhile, part-time faculty are now more than 40 percent of college instructors, as shown by the line soaring towards the top of the graph.