Four years ago, two of the most influential researchers in higher education dove into a huge pool of data hoping to answer a bedeviling question: Why do so many students who start college fail to graduate?

They report their findings in a book released this week, and perhaps the biggest is this: Students aren't aiming high enough, settling for less selective schools they imagine will be easier, but where in fact they're more likely to drop out before earning a degree.

In ``Crossing the Finish Line,'' William Bowen and Michael McPherson, former presidents of Princeton University and Macalester College, along with researcher Matthew Chingos, chime in on what many experts consider American higher education's greatest weakness: college completion rates. By some measures, fewer than six in 10 entering college students complete a bachelor's degree, among the worst rates in the developed world.

The latest findings may surprise those caught up in the well-publicized admissions frenzy at high-end colleges who assume all students push for the most selective school they can find. But the authors focus on the phenomenon called “undermatching,'' or the surprisingly large number of well-qualified high school seniors with credentials to attend strong four-year colleges, but who chose other options instead -- less selective schools, two-year colleges, or no college at all.

They may have had their reasons, such as staying close to home or lack of money (though more selective schools aren't always pricier). But the authors argue bigger factors are ``inertia, lack of information, lack of forward planning for college, and lack of encouragement.'' The data suggest low-income and minority students, and especially those whose parents don't complete college, are especially susceptible.

For instance, examining 1999 North Carolina high school graduates who could have attended the flagship University of North Carolina-Chapel Hill or North Carolina State -- but instead went to less selective schools -- they conclude barely one-third even applied to the state's leading universities. Most of those that applied got in but went elsewhere, or nowhere.