Why does the national debt snowball?

Interest is owed on money already borrowed. Programs can be argued over every year; the interest on last year’s bonds cannot. A government that skipped it would be in default, and its next loan would cost far more. So in the Debt Snowball machine, taxes pour into a bar and the first slice, in coral, goes to the lenders before anything reaches programs.

In fiscal 2026 that slice was $1.14 trillion, CBO’s monthly budget review shows, against $916 billion for defense. Interest has been larger than the military budget for two years running.

Taxes brought in $5.4 trillion. After interest, $4.3 trillion was left. Programs, from Social Security and Medicare to the military, cost $6.3 trillion. The $2 trillion gap is borrowed by selling Treasury bonds, and every dollar borrowed lands on the pile.

The pile is debt held by the public: about $32.4 trillion at the end of fiscal 2026, roughly the size of the whole economy, the American Action Forum notes from Treasury’s final monthly statement. The number on New York’s debt clock is larger because it also counts what the government owes its own trust funds.

Two engines run at once. The first is the gap before interest: spend more than you take in, and the pile grows. In the model that gap is about 2.6% of GDP a year.

The second is the interest itself. The pile grows by the gap plus the interest on the pile, so a bigger pile means a bigger first slice next year, less left for programs, and more borrowing. Whether that outruns the economy comes down to one comparison, the debt-dynamics identity: the interest rate on the pile against the growth rate of the economy. Today the average rate on the debt is about 3.5% and the economy grows about 4% a year in dollar terms, which just about holds the ratio steady before the gap is counted.

Raise the rate two points, to 5.5%, and the pile outgrows the economy on its own. In the model, interest reaches nearly $4 trillion by 2036, almost half of all taxes.

1. 1 See

   Open Debt Snowball at Today, 2026. The ledger reads taxes $5.4T, interest first $1.1T, left $4.3T, programs $6.3T, borrowed $2.0T.

2. 2 Change

   Tap Rates up 2 points. By 2036 the first slice is $3.8 trillion, 47% of taxes, and the pile passes 240% of GDP by 2056.

3. 3 Understand

   Tap Balanced before interest, rate above growth. The gap is gone, and the pile still outgrows the economy. That is the second engine on its own.

Debt Snowball keeps taxes and spending at fixed shares of GDP, so there are no policy changes, recessions or inflation surprises. It applies one average rate to the whole pile at once; in reality new rates reach the pile as old bonds roll over, which takes years. The 2036 and 2056 figures are the model’s projection at the settings you choose, not a forecast.

A country is not a company. It borrows in its own currency, so it cannot run out of dollars the way Toys “R” Us ran out of cash. Its endings are different: higher taxes, less spending, inflation that shrinks the pile in real terms, or lenders demanding higher rates, which feeds the second engine. Ray Dalio’s How the Economic Machine Works, which inspired the trilogy, calls the painful version a deleveraging. The film opens on the National Debt Clock, by @newyorkcityclocks, credited on screen; the numbers come from CBO, Treasury and the model, not from the clip.