There are plenty of ways to tally up the US government’s federal debt. The total Treasury debt outstanding was about $16.74 trillion at the end of July. But the US owes about $4.84 trillion to itself, mostly in the form of debt that is issued to entities such as the Social Security trust fund. So many analysts tend to focus on the $11.91 trillion in debt that is publicly available to be traded.
As we noted earlier this week, the recent revision of US GDP—which boosted the size of the world’s largest economy by about $590 billion in 2012—instantly shrank the debt-to-GDP ratio to less than 70%. That debt load looks downright manageable if you compare it to burdens on the books of troubled European countries, for example.
But that’s just the stuff that’s “on the books.” Like many countries, the US has large stockpile of potential and actual liabilities that don’t show up on as actual debt outstanding. In fact, a new working paper by University of California-San Diego economics professor James Hamilton estimates that the US was on the hook for more than $70 trillion in off-balance sheet liabilities at the end of 2012. Yes, trillion.