How many students are actually graduating from America's colleges and universities? 

Tracking that number is becoming more important as lawmakers and the Obama administration want to tie university funding to outcomes like college completion rates.

Researchers from the National Student Clearinghouse find of the 2.4 million students who enrolled in the fall of 2007, 56 percent of them finished a degree or certificate within six years. That includes 43 percent of students who finished at the school where they started, and another 13 percent who transferred.

"A growing number of students are graduating somewhere else, and they're not being picked up by the standard graduation rate numbers," said Dr. Doug Shapiro, who led the research.

The Clearinghouse collects its data from 95 percent of all postsecondary institutions. As members of Congress and the Obama administration hope to hold colleges and universities more accountable, Shapiro said regulatory efforts won't be effective if the country fails to count most of the students who make their way through college.

"A quarter of all the students who graduated in this cohort that we tracked did not graduate from their starting institutions," Shapiro explained. "So a quarter of all the student success out there is not being picked up by these standard graduation rate numbers."

Unfortunately, Shapiro said, standard measures of college and universities are still tied to the traditional college experience - spending four years living in a dormitory while enrolled full-time on a liberal-arts college campus. "Most students today are enrolling at two or three institutions. They're going to work. They're taking care of family responsibilities. There are all kinds of variants on the student educational pathways."

The national college completion agenda is being pushed by political leaders as well as foundations. Lumina Foundation has set a goal to have 60 percent of adults earn a college credential by 2025.