My favorite bit from the article is this:
Dr. Ehrenberg and a colleague analyzed 15 years of national data and found that graduation rates declined when public universities hired large numbers of contingent faculty.
Several studies of individual universities have determined that freshmen taught by many part-timers were more likely to drop out.
These two statistics should be more prominently displayed. There is a real impact on students--not just the institution or the teachers--when the type of teacher changes!