DOUBLING TIME = 72/rate of interest
Math can be a real bitch.
The numbers behind this story come from the Wall Street Journal, “National Debt Is Projected To Nearly Double in 30 Years,” (paywall) 3/30/17. For a Zero Hedge summary, see “CBO Warns Of Fiscal Catastrophe As A Result Of Exponential Debt Growth In The U.S.”
The Congressional Budget Office (CBO) released figures this week on the government’s deficits and the national debt that are downright scary. Unfortunately, they’re not nearly scary enough. The assumptions the CBO incorporates are optimistic and will almost certainly be undercut by reality.
The headline projection was the national debt will almost double in 30 years. Using the rule of 72, T=72/r, where T is the time in years required for principle to double and r is the annual interest rate compounded, a 30-year doubling time implies the debt is growing at 2.4 percent annually (30=72/2.4). However, the national debt almost doubled during George W. Bush’s two terms, and almost doubled again during Barack Obama’s two terms. That implies a T of a little more than 8 years. To be conservative (because debt almost doubled but not quite), round the T up to 9 years. Plug that into the rule of 72, and you have the debt growing at 8 percent per year (9=72/8), or over 3.3 times the rate the CBO is assuming. Scary as that 30-year doubling sounds, simply extrapolating the reality of the last 16 years projects another doubling in not 30, but 9 years, or a year longer than Donald Trump’s potential two terms.
But wait, there’s more. The CBO assumes the 10-year Treasury rate will be 1.5 percent after inflation over the long term, but last year that rate was 1.9 percent and the year before, 2.2 percent. Ask yourself, with exploding debt and an increasing supply of Treasury bills, notes and bonds, are real rates (the interest rate after inflation) likely to go higher or lower? The CBO says lower; SLL says higher. The CBO also assumes that potential GDP will grow at 1.9 percent per year over the long term, although it grew an estimated 1.6 percent last year. Ask yourself, with debt service consuming an ever larger share of the GDP (see next paragraph), will that help or hamper economic growth? The CBO says it will help; SLL says it will hamper. Finally, the CBO assumes that net interest costs will average 2.1 percent of the GDP over the next decade, although last year they were 2.5 percent. Again, ask yourself, will a rising national debt lead to more or less debt service cost relative to the GDP? The CBO says less; SLL says more.
Even the too rosy CBO numbers paint a grim picture. It projects that debt service’s share of total federal spending will triple, from the present 7 percent to 21 percent, over the next 30 years. In the same time frame, the national debt as a percent of the GDP will increase from 77 to 150 percent.
President Trump wants to spend “yugely” on infrastructure, increase the military’s budget, cut taxes, and not touch entitlement spending. This is all pure fantasy; it’s simply not going to happen. Something’s got to give, and it will probably start in the bond market. Indeed, it probably already has; the 10-year Treasury rate reached generational lows last July and interest rates have been in an irregular uptrend since. So if you read the Zero Hedge CBO post and are feeling glum, cheer down; you’re not feeling glum enough. Unfortunately, this is not an April Fools gag.