What percentage of Americorp education awards are unused by the end of the seven year period?

I’m wondering what percentage of all the award money nationally that goes unused during the seven year period and is thus, I’m guessing, used to provide even more americorp educational awards for future Americorp participants (the awards can be used to cover past qualifying educational loans or ed loans taken out within seven years of completing the americorp program). I did an unsuccessful, but brief search, and thought I would check here to see if there is anybody from “the inside” that might have that info. Thanks.