Carl Conetta. Project on Defense Alternatives, 05 February 2010.
http://www.comw.org/pda/1002BudgetSurge.html

Federal Debt as Percent of Gross Domestic Product

Excerpt:

The most ready comparison to America’s current circumstance are the years of the Second World War. Back then, the level of debt rose higher than it has today, but the period during which the burden exceeded 100% of GDP lasted only 4 years. Today, by contrast, it looks as though the period during which debt will equal or exceed 100% of GDP will last for more than twice as long. If we think of the mid-1940s as representing “the Mount Everest” of US debt accumulation, then the period after 2008 should represent “the Tibetan plateau” (which is not as high as Everest, but far wider.)