In "Where A Is Ordinary: The Evolution of American College and University Grading, 1940–2009," Stuart Rojstaczer and Christopher Healy, examine data on the awarding of A–F letter grades at over 200 four-year colleges and universities over the past 70 years. The findings:
Contemporary data indicate that, on average across a wide range of schools, A’s represent 43% of all letter grades, an increase of 28 percentage points since 1960 and 12 percentage points since 1988. D’s and F’s total typically less than 10% of all letter grades. Private colleges and universities give, on average, significantly more A’s and B’s combined than public institutions with equal student selectivity. Southern schools grade more harshly than those in other regions, and science and engineering-focused schools grade more stringently than those emphasizing the liberal arts. At schools with modest selectivity, grading is as generous as it was in the mid-1980s at highly selective schools. These prestigious schools have, in turn, continued to ramp up their grades. It is likely that at many selective and highly selective schools, undergraduate GPAs are now so saturated at the high end that they have little use as a motivator of students and as an evaluation tool for graduate and professional schools and employers.The authors conclude that "A has become the most common grade on American college campuses. Without regulation, or at least strong grading guidelines, grades at American institutions of higher learning likely will continue to have less and less meaning."
Figure 1, "Distribution of grades at American colleges and universities as a function of time," gives a nice overview of what has happened:
The number of Bs, Ds, and Fs have changed a little, but are generally in the same range. The number of Cs awarded, on the other hand, dropped as dramatically as the number of As awarded rose. Many students who used to get Cs must now be getting As.
One big question is what caused this change? The article discusses various possibilities at some length and concludes, humiliatingly for us professors, that we have lowered our standards. If that is true, the question of grade inflation may be tied to the assessment regime we all now live under and mostly loathe. Lower standards would of course mean that students will learn less, and the fact that so many students are being graduated without the skills employers need is an important driver of assessment.