[DuncanWaring]

Exhibit a is the fact that under the Obama administration’s current fiscal plans, the national debt in the US (on a gross basis) will climb to above 100pc of GDP by 2015 – ...

If one includes in the "National Debt" figures the "Social Security Trust Fund", the national debt is already very close to 100% of GDP and will reach 100% well before 2015.

The fact that said trust fund is called an "Intergovernmental Holding" doesn't change the fact that it's still a debt.

Borrowing money from your parents instead of a bank doesn't mean you're not in debt.

[remember]

If one includes in the "National Debt" figures the "Social Security Trust Fund", the national debt is already very close to 100% of GDP and will reach 100% well before 2015.

You're correct. The red line in the following graph shows the projected gross federal debt through 2015 as given in the most recently released U.S. budget:

The actual numbers and sources can be found at this link. As can be seen, the gross federal debt is projected to reach 94.3% of GDP by the end of 2010, 99% of GDP by the end of 2011, and 100.8% of GDP by the end of 2012. It is projected to continue increasing after that, reaching 102.6% of GDP by the end of 2015.

The fact that said trust fund is called an "Intergovernmental Holding" doesn't change the fact that it's still a debt.

Agreed. In any event, it will all become debt held by the public soon enough as Social Security cashes in its bonds. Hence, the long-run budget projections from the 2011 Budget project that the debt held by the public will reach about 830% of GDP by 2085! That's over 7 times the prior record reached at the end of World War II. Of course, something will have to give long before we reach that level of debt.