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Millennials aren't the only ones drowning in student debt: A staggering amount of older Americans are also underwater. The number of Americans older than 60 with student loan debt quadrupled from 700,000 in 2005 to 2.8 million in 2015, making the over-60 set the fastest-growing age group with student debt, Quartz reports. The total debt for these older borrowers is some $66.7 billion, and more than two-thirds of it is owed for children or grandchildren. While older debtors owe less than the typical under-50 crowd — an average of $23,000 compared to $37,172, respectively — they're also twice as likely to default.

Quartz notes the particular dangers of being 60 or older and still carrying that much debt: The government can sometimes withhold Social Security checks to elderly borrowers who default, and Americans over 60 with unpaid loans typically have less saved for retirement than those without debt.