The Government’s Borrowing Tab Keeps Growing, Month by Month

The average interest rate the US government pays on its Treasury bonds rose to 3.466% in September, up from 3.453% in August. Small move, but look at the six-month trend: the rate has climbed every single month since April, rising 0.063 percentage points in a straight line.

This is the compounding math of a large debt load meeting a higher rate environment. The US doesn’t refinance all its debt at once. It rolls over maturing bonds gradually, replacing older, cheaper debt with new bonds issued at today’s rates. Each month that market rates stay elevated, the average cost of the entire debt portfolio inches higher. It’s a slow ratchet, and it only turns one way until rates fall and stay down long enough to reverse it. Year over year, the average rate is up 3.59%, a quiet but persistent rise.

The broader picture here matters. The economic gauges show that monetary policy remains restrictive by historical standards and long-term interest rates sit in the upper range of their history. Neither has broken decisively lower. That means the government’s debt service costs will likely keep grinding higher as old, low-rate bonds mature and are replaced at today’s levels.

Historically, when the average rate on government debt rises steadily in a high-rate environment, two things follow for businesses and investors: the “risk-free” rate on competing assets stays firm (which affects how all other assets are priced), and fiscal pressure builds over time (which raises questions about future tax and spending policy). In past cycles, investors and capital allocators have watched this number alongside the deficit trajectory to gauge how much supply of new Treasury bonds might be coming to market.

Bottom Line: The US government’s average borrowing cost has risen every month for six straight months. The question going forward is whether rate relief arrives before the rollover math becomes a more serious drag on the fiscal picture.

Source: US Treasury Fiscal Data

ON1010 Research is an independent publisher of economic education and is not a registered investment adviser, broker-dealer, or investment company. This content is for educational and informational purposes only and is not investment advice or a recommendation to buy, sell, or hold any security. Published under the publisher exemption recognized by Section 202(a)(11)(D) of the Investment Advisers Act of 1940 (Lowe v. SEC). Always consult a qualified financial professional before making any financial decision.