Part of the gross national debt includes the entire $1.5 trillion Social Security Trust Fund, all of which has been borrowed and spent. Since the early 1980s, U.S. taxpayers have been paying extra FICA taxes to build up a surplus that will have over $3.5 trillion by 2012 and an even higher amount in its peak year of 2017.  But this surplus has been loaned to the General Fund of the federal government for other uses, contributing even further to the national debt. (more)