An empire at risk

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.

This matters more for a superpower than for a small Atlantic island for one very simple reason. As interest payments eat into the budget, something has to give—and that something is nearly always defense expenditure. According to the CBO, a significant decline in the relative share of national security in the federal budget is already baked into the cake. On the Pentagon’s present plan, defense spending is set to fall from above 4 percent now to 3.2 percent of GDP in 2015 and to 2.6 percent of GDP by 2028.

Over the longer run, to my own estimated departure date of 2039, spending on health care rises from 16 percent to 33 percent of GDP (some of the money presumably is going to keep me from expiring even sooner). But spending on everything other than health, Social Security, and interest payments drops from 12 percent to 8.4 percent.

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.