Here’s one way to look at it: We’re looking at a rise in the debt/G.D.P. ratio of about 40 percentage points. The real interest on that additional debt (you want to subtract off inflation) will probably be around 1 percent of G.D.P., or 5 percent of federal revenue. That doesn’t sound like an overwhelming burden.
Now, this assumes that the U.S. government’s credit will remain good so that it’s able to borrow at relatively low interest rates. So far, that’s still true. Despite the prospect of big deficits, the government is able to borrow money long term at an interest rate of less than 3.5 percent, which is low by historical standards. People making bets with real money don’t seem to be worried about U.S. solvency.
The numbers tell you why. According to the White House projections, by 2019, net federal debt will be around 70 percent of G.D.P. That’s not good, but it’s within a range that has historically proved manageable for advanced countries, even those with relatively weak governments. In the early 1990s, Belgium — which is deeply divided along linguistic lines — had a net debt of 118 percent of G.D.P., while Italy — which is, well, Italy — had a net debt of 114 percent of G.D.P. Neither faced a financial crisis.
So is there anything to worry about? Yes, but the dangers are political, not economic.