Only one in five of those who enroll in two-year institutions earn an associate degree within three years, and only two in five of those who start four-year colleges complete their degrees within six years.  A new report, “With Their Whole Lives Ahead of Them,” issued by Public Agenda, a non-partisan research group, shatters some of the myths about why students drop out of college, and offers interesting solutions such as

"One set of solutions might revolve around making part-time attendance more viable by giving those
students better access to loans, tuition assistance and ealth care—benefits and services that are frequently
available only to full-time students.

The report is summarized in this New York Times article.