Input substitution and grade inflation :: Economist's View

Mark Thoma notes a connection between job security and grade inflation:

During the time grades were increasing, budgets were also tightening inducing a substitution towards younger and less permanent faculty. I broke down grade inflation by instructor rank and found it is much higher among assistant professors, adjuncts, TAs, instructors, etc. than for associate or full professors. These are instructors who are usually hired year-to-year or need to demonstrate teaching effectiveness for the job market, so they have an incentive to inflate evaluations as much as possible, and high grades are one means of manipulating student course evaluations.