U.S. Debt Obligations $70 Trillion

The study's $70 trillion debt estimate may actually be overly optimistic. Boston University economics professor Laurence J. Kotlikoff, who served on President Ronald Reagan’s Council of Economic Advisers, says the nation’s true debt obligations are three times that figure.
"If you add up all the promises that have been made for spending obligations, including defense expenditures, and you subtract all the taxes that we expect to collect, the difference is $211 trillion. That's the fiscal gap," Kotlikoff told National Public Radio. "That's our true indebtedness."