<p>Students drop out or leave college for a variety of reasons. As you go farther down on the scale of selectivity, you are also going farther down on the economic scale – but of course college that are less selective also tend to have less funding available for need-based aid. So there is going to be an ever-increasing number of students who leave school for economic reasons. </p>
<p>I also think that at least for the UC system, the reported stats are missing a huge part of the picture by failing to account for the large number of students who come in as junior year transfers after community college – that is an extremely common path to a 4-year degree in college, again among those who are faced with economic barriers. </p>
<p>Rather than draw unwarranted assumptions from raw statistics, why don’t you see if you can correlate 4-year graduation rates to the percentage of students who reside on campus? or correlate graduation rates with percentage of Pell grant recipients? You seem to assume that most students want to attend university continuously for 4 years— but I don’t think that path makes economic sense for many.</p>