I think this is an interesting essay explaining the prevalence of grade inflation (and mentioning a way to combat it) -- it is the path of least resistance for professors and teaching assistants.

http://qz.com/157579/confession-of-an-ivy-league-teaching-assistant-heres-why-i-inflated-grades/
Confession of an Ivy League teaching assistant: Here’s why I inflated grades
By Allison Schrager
Quartz
December 13, 2013

Quote
I did my undergraduate work in Britain, where grade inflation is less of a problem. That’s because the brunt of your grade came from a single essay at the end of the year. These exams are double marked, by your professor and one at another university, to ensure uniform national standards. That not only kept grade inflation in check, but the culture of complaining too. I would have been considered presumptuous to question the judgment of two professors.

That may not be realistic at research universities in America, as the British grading system is very time intensive and universities there are more teaching and less research oriented. But it’s worth consideration as US colleges grapple with keeping standards, one campus to another.