New data on grade inflation in American colleges

Catherine Rampell is reporting this morning (see here) on a new paper by Stuart Rojstaczer and Christopher Healy (see their website here) detailing the history of grade inflation in American colleges and universities.  One of the graphs from the paper (see below, click to enlarge) essentially tells the story.

 Mr. Rampell says of the graph:

As you can see, public and private school grading curves started out as relatively similar, and gradually pulled further apart. Both types of institutions made their curves easier over time, but private schools made their grades much easier.