Citations:
[1] http://nces.ed.gov/programs/digest/d13/tables/dt13_330.10.asp
[2] http://libertystreeteconomics.newyorkfed.org/2012/03/grading-student-loans.html
[3] http://chronicle.com/article/Tuition-Increases-Slow-Down/142547/
[4] http://www.newyorkfed.org/research/staff_reports/sr668.pdf
[5] http://libertystreeteconomics.newyorkfed.org/2012/03/grading-student-loans.html#.VFksG_nF-So