Earlier quoted context omitted.
Less than half of the students from my alma mater graduate within four years. When I learned this I was dumbfounded. The incentives are just not correctly aligned. The university is able to profit off of students taking fewer credit hours and staying more semesters, and academic advisors actively encourage this!
I learned (when MIT shut down my former dorm) that they track the six year graduation rate (doubt anyone is attending all of the six years). That seems more sensible.
(I won't spoil the joke, google it!)
As I recall, only a small handful took 5 years. This drifting along failing to graduate seems to be a modern phenomenon.