Marginal Revolution recently linked to an interesting report on grade inflation by economist Mark Thoma. The data itself is fairly clear: Average GPAs stabilized in the ’70s and ’80s after a massive upward trend likely due to the Vietnam War draft. Then grades started drifting upwards again, for less obvious reasons, starting in the early ’90s. Thoma’s analysis of the data suggests an explanation that I’ve never heard before:

My study finds an interesting correlation in the data. 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.

Even if younger teachers in fairly tenuous positions are largely responsible for the recent upward trend in grades, even a subconscious desire to bribe the students into good evaluations is hardly the only possible explanation for it. (I’m particularly skeptical given that evaluations are often done a week or two before the end of the semester, when students don’t yet know their final grade, but only their grades on early exams and/or papers.)

So here’s another possibility: Due to their lack of experience, newer teachers are less likely to have the skills required for doling out low grades, such as a finely-honed detector of student bullshit, a cultivated indifference to the self-created problems of irresponsible students, an adequate understanding of all that a diligent student is capable, confidence in the justice of the grades awarded, strategies for putting off pushy students, and so on. Those skills can be difficult to cultivate, even for teachers committed to actually educating their students. Of course, honest educators will develop them with time. In contrast, second-handers who primarily seek to be liked by their students, whether in exchange for high evaluations or not, will not.

The unpleasant results of the inexperienced teaching the lazy but demanding seems fairly evident in this Washington Post article on grade inflation. I suspect the real culprit has not yet been identified.