The Chronicle had an article on just that topic.
From the 1970s to the 1990s, the proportion of students who completed a bachelor’s degree in four years shrank by 13 percentage points, said Sarah Turner, a professor of economics and education at the University of Virginia and the author of the research.
These days earning a bachelor’s degree takes at least five years, Ms. Turner said.
The decline, however, was found mostly at public four-year universities that are not flagship institutions, she said. In fact, at highly selective private institutions, the number of students completing their degrees in four years increased by 8 percent between 1972 and 1992.
“This is very much a story of stratification,” Ms. Turner said.
One explanation for the decline at public colleges, Ms. Turner suggested, is that students today often find it hard to finance their educations and have to work during college. Work is crowding students’ time to take courses.
Unlike what I pointed out yesterday, this article makes a good argument for tracking and retention.
Working students tend not to have strong high-school backgrounds and usually attend college part time rather than full time, he said. “Yet we put them into the same system as other students and are disappointed that we don’t get good results.”
Mr. Jones advocates scheduling classes in a convenient block of time to make it easier for students with work and family commitments to attend and help them graduate faster.
This is interesting and relevant to my whole point on socioeconomic class and culture having a lot to do with how successful students in general are in college.