We’ve written before about some of the work of Stuart Rojstaczer and Christopher Healy, grade inflation chroniclers extraordinaire. They have put together a new, comprehensive study of college grading over the decades, and let me tell you, it is a doozy.

The researchers collected historical data on letter grades awarded by more than 200 four-year colleges and universities. Their analysis (published in the Teachers College Record) confirm that the share of A grades awarded has skyrocketed over the years....

Most recently, about 43 percent of all letter grades given were A’s, an increase of 28 percentage points since 1960 and 12 percentage points since 1988. The distribution of B’s has stayed relatively constant; the growing share of A’s instead comes at the expense of a shrinking share of C’s, D’s and F’s. In fact, only about 10 percent of grades awarded are D’s and F’s.As we have written before, private colleges and universities are by far the biggest offenders on grade inflation, even when you compare private schools to equally selective public schools....