I think you're confused. According to the text I quoted, it's not the case that student loans delinquencies are hidden, and so students take on even more student debt to get an even more expensive degree and presumably a shot at an even higher paying job. No, instead they go and buy more expensive cars and houses. If you take on as much debt as you can for the purpose of consumption, you're shit with money. The fact that grads make more money than non grads is irrelevant here.