I found an article where they plan to do a study to try to identify the appallingly low graduation rates from four year universities - http://www.cnn.com/2005/EDUCATION/11/16/colleges.graduating.ap/index.html.
I wonder if they'll even remotely connect age as a factor of graduation? So many kids these days are only going to school because the parents say they must - even if they believe they must. But then they do so poorly in class (even when they pass with A's) because they aren't interested in learning more by classroom. They want to go out in the world and start living it. When students have done that and then decide they want to go back to school because now they know what they want to do - they have a MUCH harder time getting started (i.e., between work, family, bills, lack of financial assistance, etc). But, once they start - they do tend to do so much better.
I know when I was teaching my best students were all over 25. I wish I had a way to give my son the opportunity to grow up a little more before he started school.