Debt and empire

Already, the federal government's interest payments are forecast by the CBO to rise from 8 percent of revenues in 2009 to 17 percent by 2019, even if rates stay low and growth resumes. If rates rise even slightly and the economy flatlines, we'll get to 20 percent much sooner. And history suggests that once you are spending as much as a fifth of your revenues on debt service, you have a problem. It's all too easy to find yourself in a vicious circle of diminishing credibility. The investors don't believe you can afford your debts, so they charge higher interest, which makes your position even worse. ...

As interest payments eat into the budget, something has to give—and that something is nearly always defense expenditure. ...

This is how empires decline. It begins with a debt explosion. It ends with an inexorable reduction in the resources available for the Army, Navy, and Air Force. Which is why voters are right to worry about America's debt crisis. According to a recent Rasmussen report, 42 percent of Americans now say that cutting the deficit in half by the end of the president's first term should be the administration's most important task—significantly more than the 24 percent who see health-care reform as the No. 1 priority. ...

The precedents are certainly there. Habsburg Spain defaulted on all or part of its debt 14 times between 1557 and 1696 and also succumbed to inflation due to a surfeit of New World silver. Prerevolutionary France was spending 62 percent of royal revenue on debt service by 1788. The Ottoman Empire went the same way: interest payments and amortization rose from 15 percent of the budget in 1860 to 50 percent in 1875. And don't forget the last great English-speaking empire. By the interwar years, interest payments were consuming 44 percent of the British budget, making it intensely difficult to rearm in the face of a new German threat.

--Historian Niall Ferguson, Time, on how finance brings down empires