According to The Atlantic, student loans have grown 511% since 1999. That is a staggering amount (well above inflation, obviously, as well as the growth in number of students), but it's also striking because it outpaces the growth in household debt by a longshot:
This chart looks like a mistake, but it's correct. Student loan debt has grown by 511% over this period. In the first quarter of 1999, just $90 billion in student loans were outstanding. As of the second quarter of 2011, that balance had ballooned to $550 billion.
The chart above is striking for another reason. See that blue line for all other debt but student loans? This wasn't just any average period in history for household debt. This period included the inflation of a housing bubble so gigantic that it caused the financial sector to collapse and led to the worst recession since the Great Depression. But that other debt growth? It's dwarfed by student loan growth.