Accidentally I found the following (not-so-new) quote from internet.
‘Less than 2 percent of grades given at elite institutions are D's or F's, and that at schools such as Pomona, Duke, Harvard and Columbia, about half of all grades are A's. … Harvey Mansfield Jr., a Harvard government professor, has tried on his own to draw attention to the problem by giving his students two grades — one that's officially reported for transcripts and another, lower, that reflects what he feels they truly earned. "I remember when a B was an honors grade — today a B-minus is a slap in the face," Mansfield says. "I still give two grades. When I stop, that's when you'll know we've started to make progress."’
Let’s face it. Who on earth (or on campus?) will care if I assign two grades – one nominal and another real?
The website created by Stuart Rojstaczer, a professor of environmental science at Duke, www.GradeInflation.com, contains very interesting data of many universities in USA. [For instance, at Purdue, GPA ave is 2.71 in 1980 and 1990; 2.81 in 2006. At Princeton, ave is 3.13 in 1980; 3.22 in 1990; 3.27 in 2006. At FIU, ave is 2.72 in 2006. At Cornell, ave is 3.13 in 1990; 3.36 in 2006. At Harvard, ave is 3.05 in 1975; 3.30 in 1990; 3.45 in 2005. At Vanderbilt, ave is 3.28 in 2006. At Nebraska-Lincoln, ave is 3.07 in 2006. At Duke, ave is 3.02 in 1980; 3.21 in 1990; 3.42 in 2006. At U. of Oregon, ave is 2.95 in 1992; 3.10 in 2004. At U. of Minnesota, ave is 2.77 in 1970; 2.88 in 1980; 2.83 in 1990; 2.95 in 1997. At Middlebury, ave is 3.10 in 1990; 2.29 in 2000; 3.34 in 2004. At Lehigh, ave is 2.6 in 1972; 2.97 in 2000; 3.15 in 2007. At Ohio University, ave is 2.66 in 1986; 2.82 in 1990; 3.01 in 2004.] Now I remember why, as a graduate student in the 80s, I was so eager to study at places such as Purdue and Minnesota. Professor M. Watts, who was the course coordinator while I served as a graduate instructor, did a good job then (and afterwards).
The following links might be of some interest.
Another research topic is the teaching evaluation inflation.