Well..that is because more students are going to College...instead of manual labor..etc. Direct result of the manufacturing industry and other labor...ie steel...coal..textile...etc..etc. Other factors as well..ie birth rates. but the main reason is what I cited above.

So that is why the debt is growing...refer to this chart:

http://nces.ed.gov/programs/digest/d13/tables...302.60.asp

More kids going enrolling into school ...instead of the trades....etc