Albert Einstein is often quoted as saying that compound interest is “the most powerful force in the universe.” The quote is probably apocryphal, but it reflects a mathematical truth. Interest on earlier interest grows exponentially, outrunning the linear growth of revenue and eventually consuming everything.
That is where the United States now stands. The government does pay the interest on its debt every year, but it is having to pay it with borrowed money. The interest curve is rising exponentially, while the tax base is not.
Interest is now the fastest growing line item in the entire federal budget. The government paid $970 billion in net interest in FY2025, more than the Pentagon budget and rapidly closing in on Social Security. It already exceeds spending on Medicare and national defense and is second only to Social Security. The Congressional Budget Office projects that interest will reach nearly $1.8 trillion by 2035 and will cost taxpayers $13.8 trillion over the next decade. That is roughly what Social Security will pay out over the same decade (about $1.6 trillion a year). The Social Security Trust Fund is running dry, not because there are too many seniors, but because interest payments are consuming the federal budget that should be shoring it up.
