Who holds America’s 1.5 trillion student loan debt?

From The Chronicle: “In 2007, there were 28.8 million borrowers. At the end of 2017, almost 45 million people held student-loan debt, more than the population of California. … Although the majority of student loans are held by the federal government, gathering details on who actually holds this debt is rather complicated. … The majority of this debt is held by students. Only about 6% of the total outstanding amount is held by parents. … The largest portion of outstanding federal student-loan debt was incurred to attend public institutions…While less of the debt was incurred at private nonprofit institutions versus public ones, borrowers from these institutions hold more debt on average. For-profit institutions had the lowest mean debt, at $20,869.