Market value of Federal Debt doubles in a very short time

These data reveal that the market value of gross Federal debt (including Fed and SS Trust fund holdings) doubled between 9/2003 and 9/2010 (going from $7,303.2 to $14,497.4), and the market value of privately held Federal debt doubled since 9/2005 (going from $3,982.9 to $7,979.3). Sooner or later, the income tax will have to be raised in order to pay off this runup in debt. At the same time, the carrying cost of that debt is barely 2% of GDP, almost half of which is paid to foreigners.