The average student debt for new graduates crept up 2 percent in 2013, to $28,400, according to a new report by the Institute for College Access and Success (ICAS). But that number can range from an average low of $18,656 in New Mexico to a high of $32,795 in New Hampshire -- one of six states where average student debt tops $30,000. 

ICAS calculates each state's average based on data that is voluntarily reported by public and nonprofit four-year colleges in those states. The schools that chose to respond to the ICAS survey awarded 83 percent of bachelor's degrees conferred in the 2012-2013 academic year.

For-profit colleges don't count in the mix because so few of them choose to report debt levels to ICAS -- although their graduates hold an average 43 percent more debt than graduates from other types of four-year colleges, according to an ICAS analysis of U.S. Department of Education data.

“Generally speaking, public colleges have lower tuition and lower debt," Debbie Cochrane, the research director at ICAS, says. "So a state that relies more heavily on public colleges might have lower debt.”

For instance, in New Mexico, "98 percent of their graduates were from public colleges," Cochrane says, "and their public college graduates have low-average debt."  

Similarly California, the No. 2 low-debt state, relies relatively heavily on public colleges, "but there's also a state grant program that's quite generous for university students," says Cochrane.

Yet "no one factor" explains high- and low-average debt levels across the board, Cochrane says. For example, take two high-debt states, Delaware (No. 2 on the list) and Rhode Island (No. 4 on the list). 

Delaware tells a story of a large proportion of students paying out-of-state tuition. Cochrane tells IBTimes that in Delaware, 64 percent of the beginning freshman at public colleges are paying out-of-state tuition -- more than four times the national average of 15 percent. 

In Rhode Island, though, Cochrane notes another trend. In that state, 63 percent of graduates earn degrees from private nonprofit colleges -- which, again, tend to be more expensive and produce higher debt, than public schools.

But even low averages are not necessarily an indicator of how individual students will handle that debt down the road. According to data from the Department of Education, New Mexico federal student loan borrowers have one of the highest default rates in the country, as measured among students who defaulted within three years of starting the repayment process.

"In many cases, default is actually not correlated with high debt loads, but rather completion," Cochrane says. In other words, a student who graduates might have more debt than a person who leaves school after only one year -- but the graduate, armed with a degree, would be in a better position to pay back that debt.

The ICAS report also stresses the need for better data collection on how much student loan debt graduates leave college with, so consumers can make better decisions.

“Student debt has become too prominent of an issue, and too important of an issue, for us to be relying on voluntarily self-reported data that is so limited,” Cochrane says.