Income-based repayment plans, wherein monthly loan payments are reduced depending on the strained finances of students, have ballooned in popularity, growing by more than 50 percent since a year ago. Almost 4 million borrowers have entered IBR plans, according to The Atlantic. After 20 or 25 years, the outstanding debt is forgiven, leaving the public to foot the bill.

As a program for undergraduate students, some cost controls limit expenses. Dependent students can only borrow up to $31,000 for undergraduate studies and independent students can receive up to $57,500.

Graduate students, however, qualify for up to $138,500 in federal Stafford loans that include any undergraduate federal loans they received. If a student maxes out their Stafford loans for undergraduate studies, they can receive another $81,000 for graduate studies.

If a student needs more, a graduate PLUS loan is another federally guaranteed loan that covers other costs of graduate school. A graduate student, then, can fund tuition, living expenses, and any other costs of graduate school with federal loans.

That availability has led to graduate student loans becoming a large chunk of total student debt.

Graduate students “now account for roughly 40 percent of all student debt but represent just 14 percent of students in higher education,” according to The Wall Street Journal.

At public four-year colleges, 59 percent of undergraduates borrowed loans in 2012-2013 averaging to $25,600 per borrower, according to the College Board. It’s a 20 percent increase from a decade ago, but it’s still a manageable — if undesirable — chunk of debt over five or 10 years.

With 2 million borrowers holding $100,000 or more in debt, and $200 billion in loans entering IBR programs, as The Atlantic noted, the growing cost is a concern. Almost 10 percent of borrowers have entered IBR programs, and almost half of those borrowers were graduate students.

A decade ago, 79 percent of graduate students borrowed less than $40,000 or not at all for undergraduate and graduate studies. For the 2011-2012 academic year, that figure fell to 53 percent, according to the College Board.

As debt — and college tuition — increases for post-graduate education, it threatens the affordability of continuing education as well as the effectiveness of federal student loans. The more funding that goes toward post-graduate education, the more regressive higher education becomes.

Low-income undergraduate students have lower graduation rates and struggle to navigate the higher education system more than their richer peers. As higher education becomes more expensive, and transforms into a middle-class entitlement, the social and economic advancement that a college degree carries has become weaker.

In effect, the college system is diminishing its marginal value for low-income students while indebting graduate students with unlimited access to loans. Before long, the system will have to confront the stress.