One reason for the increase is the changing demographics of those enrolling in college. Students over the age of 25 accounted for more than 40 percent of college enrollment growth from 2000 to 2011, according to an analysis of National Center for Education Statistics data.
"More students are nontraditional now and fewer are coming to college directly from high school," said Kim Oppelt, education and outreach manager with education technology firm Hobsons. She noted that more students are also coming from the military or may be first-generation Americans — and in both cases, are expected to help support their families financially.
Students are working an average of 30 hours a week, Georgetown researchers found. But about 25 percent of working students are simultaneously employed full-time and enrolled in college full-time.
Unfortunately, the additional workload won't typically generate enough income to foot the full bill at most schools. A student working full time at the federal minimum wage would earn $15,080 annually before taxes. But college costs, which have ballooned over the past few decades, often require much more than that.
For the 2014-15 academic year, the average cost of tuition, fees, room and board at a four-year public college was $18,943 for in-state students. At private universities, the average total cost was $42,419 for the year. In 1975, those bills came to just $7,938 and $16,475, respectively, according to the College Board.
"Today, almost every college student works, but you can't work your way through college anymore," said Anthony P. Carnevale, director of the Georgetown University Center on Education and the Workforce, in a statement. "Even if you work, you have to take out loans and take on debt."
Indeed, seven in 10 college graduates in 2014 had student loans, with an average of $28,950 owed per borrower, according to the Institute for College Access and Success. Student loan balances total nearly $1.3 trillion, compared with about $370 billion a decade ago.