I've been a skeptic for some time about claims that we have a student loan "crisis" in the United States. For individuals mired with student loan debt, it is very much a crisis, of course. But my reluctance to term growing levels of student loan debt a crisis reflects the fact that student loan debt is highly concentrated within the population and is generally structured in a way that does not create sharp liquidity crises: long (and often deferrable) maturities, no sharp repayment shocks, and often offers established repayment and forgiveness programs. (This is more true of government loans than private loans.) And, while student loan debt is growing rapidly, it is still only about a 9th of the size of the mortgage market. All of this has kept the student loan kettle from boiling over.
Yet at the same time it is precisely because of the concentration of student loans in the younger population that it is concerning. Large debt loads at the beginning of one's adult life are likely to have very different effects on than debt spread out over a life time. Moreover, student loans are not incurred based on current income, but on assumptions of future income (if that), so student loan debt burdens are more likely to be poorly calibrated to borrower's actual earning capacity. Additionally, because student loan debt is not dischargeable in bankruptcy (except in extreme circumstances), unlike other types of debt, it likely to stick around. And, unlike various types of secured debt, there is no "put" option. A homeowner who runs into trouble with a mortgage or a cash-strapped auto loan borrower can always sell the house or car (or let them be repossessed) to pay off part or all of the debt. That's not possible with unsecured debt.
The real concern with student loans is not an acute liquidity crisis, like a mortgage payment resets or a massive surge in defaults, as with underwater homeowners. Instead, the systemic danger from student loans is a debt overhang problem in which consumers' consumption habits are altered by the constant drag of debt service. That's not a "crisis" yet, but it's a problem that needs to be addressed before it becomes one.