Because the Fed only sets the overnight rate, and the market sets the long ones. A central bank cut moves the short end. The ten- and thirty-year rates are prices, set by whoever has to hold that debt for decades, and they answer to inflation expectations, the supply of government borrowing, and how much compensation holders demand for the risk - not to the policy rate.
The two have been moving in opposite directions. Through the Fed's cutting cycle (the most recent cut in December 2025), short-term rates came down with the policy rate while the US ten-year went UP about 106 basis points and the thirty-year about 122. As of mid-September 2026 the US thirty-year sits at 5.37% - before this year it had not been above 5.2 since 2007 - and Europe and Japan are moving the same way at the same time, which is the tell that this is about sovereign debt itself rather than any one country's policy.
The short end has since turned, and it changes nothing in the paragraph above. By mid-September 2026 the market had moved from expecting cuts to pricing a quarter-point rise, and in September 2026 that rise was delivered. The three-month Treasury bill is at 4.19 per cent as of 23 September, against a federal funds effective rate that sat at 3.63 through August. The policy rate is the short end either way. The long end has been setting its own price throughout, which is the point of this answer and is why the direction of the next policy move does not settle what a mortgage costs.
Why it reaches you even if you never trade a bond: the long rate is what sets a mortgage, a corporate refinancing, and any project that takes years to pay for itself. So the "rate cuts" in the headlines never arrived at the borrowing that matters for households and companies - the cost of long money rose through them.
Why it reads as an alarm rather than a quirk: the chair of the Financial Stability Board named fragilities in sovereign debt markets first in his September 2026 warning letter to the G20, ahead of private credit and stretched AI valuations. Long rates rising through a cutting cycle, across the developed world at once, is the bond market repricing the debt itself.
The ten-year has since gone through 5 per cent as well. It closed at 5.11 per cent on 23 September 2026, the first time above 5 since 2007. Almost all of that rise is the real cost of money rather than an inflation view, and the split is separately measurable: how to tell which half is moving.
Figures as of late September 2026 - check current levels before quoting them onward. Related: what central banks are warning about AI valuations and whether US credit stress is already past 2007. Full write-up with the charts: https://www.tigzig.com/post/bond-markets-alarm-sep2026.
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