The percentage of A's given out in colleges and universities almost tripled between 1940 and 2008, and A's made up almost 45 percent of grades given out in 2008. The percentage of B's has dropped slightly after a peak during the 1970s and '80s, and the percentage of C's dropped sharply after 1966 and again from the late 1980s to 2008, to about 15 percent in 2008. D's and F's have dropped to less than 5 percent each after starting at about 12 percent and about 6 percent, respectively. Researchers attribute the sharp rise in grades to historical factors, such as a reluctance for professors to fail students during the Vietnam War, as well as a more consumer-based approach to education.
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