Douglas Webber is known as a "numbers guy" at Temple University in Pennsylvania.

　　Webber is a labor economist. Years ago, he met his future wife at a mathematics camp. His latest research offers guidance on how to keep students on target to earn a degree from a college or university.

　　Among his findings: It is important, whenever possible, for college students to complete their degree program in four years. Also, getting a part-time job is probably a good thing to help finance a college education. But too much time spent working on a job makes it less likely the student will graduate.

　　Webber's latest research suggests that students who are close to dropping out of school will do better financially if they "stay with it" and find a way to graduate.

　　Why is finishing college in four years so important?

　　One thing, Webber said, is financial aid that helps many students pay for college. Scholarships and other assistance generally stop after four years. So the cost of each additional year in school is likely to come almost entirely from the student and/or parents.

　　But there are other reasons why taking more than four years is a problem, as Webber notes.

　　"It's because life gets in the way, other things happen."

　　By that he means the longer you stay in college, the more likely that some unexpected event will affect your studies. It could be a loved one getting sick, a parent losing a job, or the student running out of money for college.

　　"For any number of reasons, it is in your best interest to try to get out as soon as possible."

　　It is not only that students staying in school more than four years are more likely to drop out before earning a degree.

　　"It's another year or two out of the labor market," that means lost earnings, Webber said.

　　The latest information shows a majority of college students are not earning a degree in four years. The Digest of Education Statistics considered students who entered four-year colleges in 2009. It found that only about four in 10 graduated within four years.

　　It is also important that students have enough time to complete their college classes, Webber added.

　　His research suggests part-time work of 15 hours or less will not cause harm to the student's scholastic performance.

　　But his research shows students who work 20 hours or more a week are about 15 percent less likely to graduate on time, or to graduate at all.

　　His belief is that students active in college athletic programs would face the same problem. It is common, he said, for student athletes to spend 20 hours or more for training, travel and to compete against athletes or teams from other schools.

　　University of Pennsylvania researchers looked at graduation rates for students at 65 universities with big sports programs. They found that 68.5 percent of these student athletes graduated within six years. That compared to 75 percent of all undergraduates at those schools.

　　What about struggling students?

　　Webber did his latest research with Ben Ost and Victor Pan of the University of Illinois. They looked at students who were struggling to pass their classes.

　　Webber said many people think that students who are close to dropping out of school would be better off cutting their losses and leaving without a degree.

　　But he said his team's research shows a strong return for those students who can struggle through and get a degree.

　　He looked at earnings information for people who dropped out of college. He also looked at income for graduates who were once on probation because of low grades.

　　The bottom line, he said, is that students who "persisted" and got their degree earn about $500,000 more over their lifetimes than those who gave up or were forced out of school.

　　"There is a massive difference in your earnings outcome if you're going from 119 credits (one short of graduation requirements) to 120 credits and a degree," Webber said.

　　Webber supports programs that help students meet their academic obligations. For example, he said, Temple University has a "Fly in 4" program. It provides aid to needy students so they do not have to work too long at part-time jobs to pay for college costs.

　　Webber also supports a program at Georgia State University in Atlanta. The university uses a computer program to keep watch over student performances -- so problems -- such as the failure to turn in an assignment or a low test grade -- can be fixed quickly.

　　Georgia State says it can help find solutions for struggling students before they risk flunking out.

　　I'm Jill Robbins

　　And I'm Bruce Alpert.

　　Bruce Alpert reported this story for Learning English. George Grow was the editor.

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