Angela Terrano's boyfriend was graduating. She was fighting with her roommate. And she was struggling with a math class.

And so, in 2002, she decided to leave Indiana University of Pennsylvania after her sophomore year. The plan was to move back home to Bellevue and enroll in college locally.

But plans change and, as Ms. Terrano puts it, "You expect your life to be something different than what it is."

Rather than enroll in school immediately, she decided to work for a year or two to save money. She made more money than she expected waitressing in a Downtown restaurant, and that year or two turned into five.

"I wish I'd never left IUP," she said. "I wish I'd stuck it out. I would have been done and over with it by now."

Ms. Terrano, 27, is one of more than a million people in Pennsylvania and a quarter million in the Pittsburgh metropolitan area who are older than 25 and categorized by the U.S. Census as "some college, no degree."

And like Ms. Terrano, their reasons for leaving college often defy simple explanations.

Often, students drop out because of a combination of factors -- some serious, some frivolous and some as idiosyncratic and unpredictable as college students themselves.

As part of an economic development effort, the state of Kentucky surveyed more than 1,600 "some college, no degree" folks on why they left college.

There was no one factor that the majority of respondents listed, but the most commonly cited one was "family responsibilities," followed by "financial reasons" and "offered a good job."

With 60 percent of respondents reporting a "B" average or higher when they left school, the survey noted that "a lack of academic ability or preparation was not a primary cause for leaving college."

In a nod to the variety of reasons given, Kentucky used "if life happened and your diploma didn't," as one of its marketing slogans for its "Project Graduate" program that offers assistance and incentives for students with about three years worth of credits to return to school and finish their degrees.

Philadelphia implemented a similar program earlier this year, called "Graduate! Philadelphia," which provides counseling and other services to help students return to school to complete their degrees.

For Diana Alberta, 22, of Mt. Lebanon, "life happened" when she decided to leave school to get married and have children. For Devon Conroy, 21, of Gainesville, Ga., it was a decision to leave the Pittsburgh area to go work with horses. Rhianna Moslen, 20, of Oakdale, just couldn't stand the thought of sitting in a classroom.

"At the beginning of every semester, I would beg my mom, 'Just let me stay home,' just like a little kid would do," said Ms. Moslen, who attended Geneva College, Robert Morris University and the Vet Tech Institute. "I was just tired of going to school."

Dan Burke can remember his life happening -- or more accurately, not happening -- when he dropped out of college 13 years ago. After graduating from Upper St. Clair High School, he attended Case Western Reserve University for a year, and then transferred to the University of Pittsburgh to save money.

At Pitt, "I was an awful student, I was terrible," he said. "You had to walk 25 minutes up the hills to go to class, and I was just really unmotivated."

His grade point average at Pitt was less than 1.0 on a 4-point scale, and he left after two years, working briefly as a computer programmer and then in sales.

In 1999, he returned to school part-time at Cleveland State, and then returned full time in 2005 to the University of Massachusetts-Boston and later, Middle Tennessee State, where he graduated with a degree in operations management in May.

"It was a lot more gratifying for me than it was for most of the people graduating," said Mr. Burke, 34, who is currently living in Nashville and says he finished with straight A's his final three years in school. "My experience in college was 100 percent different when I went back."

In part, that was because college had changed, too. At Pitt in the mid-1990s, older students were rare. In recent years, Mr. Burke had been surrounded by "non-traditional" students like himself.

A national study from 2002 reported that 25 percent to 30 percent of students took some time off from college and returned within six years of their initial enrollment. Another study from the same year estimated that only a quarter of students follow the "traditional" path of getting a bachelor's degree from one institution, directly after high school.

Sara Goldrick-Rab, an assistant professor at the University of Wisconsin-Madison, has studied the path of modern students through what she calls "the complex educational pipeline."

It's true that many students leave college for reasons that seem extremely personal, she said, such as not getting along with a roommate, or following a boyfriend or girlfriend. But it's also true that a student's chances of finishing college are tied to socioeconomic factors such as family income and whether their parents attended college.

"I don't think in a perfect world everybody has to start and finish," she said, "but I don't think there should be disparities based on family backgrounds."

Students in the bottom socioeconomic level are much more likely than other students to transfer from a four-year school to a community college, she said, and only 22 percent of students who do so go on to complete a bachelor's degree.

"There's not that many things that you can do that really make a dent like moving [from a four-year school] to a community college," she said. "Students should know what they're doing. They think of it as a stopping point along the way, but it tends to be that's it."

It's a battle currently under way for Ms. Terrano. After five years working in a restaurant, and realizing that she wanted to do something else with her life, she enrolled at Community College of Allegheny County in January.

Right away, she realized how much she missed learning, she said, though she also realized how much she'd forgotten in subjects such as biology and history. She completed two classes in her first term and took another class over the summer.

"I am determined to finish my degree," she said. "A high school job isn't cutting it these days."