Timothy Taylor highlights several studies which suggest that grade inflation in the humanities is causing science and math majors to change their minds:
[T]here are lots of reasons why students don't persevere in [science, technology, engineering, and mathematics (STEM)] courses: inadequate preparation at the high school level, students who have unrealistic expectations or don't want to commit the time to studying, or that the courses are just hard. It's of course possible to address these issues, but difficult. However, if one of the issues discouraging students from taking STEM courses is that grade inflation is happening faster in the humanities, then surely, this cause at least is fixable?
The Dish 