Student-loan debt is at an all-time high, with both black and white college students borrowing at record levels. But black graduates are much more likely to be saddled with large amounts of debt, according to a new analysis from the Gallup-Purdue Index, which measures the relationship between the college experience and graduates' lives.

Half of all black graduates reported taking on at least $25,000 or more to complete their undergraduate degrees between 2000 and 2014, compared to 34 percent of white graduates. That borrowing gap is a reflection of other socioeconomic disparities, says Cecilia Rouse, dean of the Woodrow Wilson School at Princeton University and an economics professor specializing in the economics of labor and education.

"It's about the fact that there is a black-white gap in income and wealth, and that's what underlies this gap in borrowing as well," Rouse says.

The average black household in the United States has less than one-tenth the accumulated wealth of the average white household. And rather than shrinking, that gulf is widening. Researchers at Brandeis University estimate that the wealth gap between blacks and whites has almost tripled over the past 25 years. So while the percentage of black and white high school graduates enrolling in college is now almost identical, black college students have far fewer resources to pay for that education.