I find this graph outlining the frequency of different grades from 1949-2009 to be enlightening [1]. Around 1940's only 15% of grades were "A", and in the last few years they went up to close to 45%.
The source data is coming from research compiled by Rojstaczer and Healy [2].
The source data is coming from research compiled by Rojstaczer and Healy [2].
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[1]: http://pazymino1evolutionliteracy.blogs.umassd.edu/files/201...
[2]: http://rampages.us/profjhonn/wp-content/uploads/sites/111/20...