On Monday 17 August, the Washington-Tehran deadline expired without an agreement, US federal debt crossed the forty-trillion-dollar threshold, and the 30-year Treasury yield closed at its highest level in 19 years — then Tokyo, Frankfurt and Paris broke their historical ceilings the following day. This research measures each ceiling broken separately, and identifies the one that was not.
The US 30-year Treasury yield closed on Monday 17 August 2026 at 5.31% — its highest official close since 2007, according to US Treasury data — after touching 5.33% intraday on Tuesday before retreating to 5.28% at the close. The break did not come from nowhere: on the same day, the Memorandum of Understanding (Memorandum of Understanding, MOU) between the United States and Iran — the 60-day truce signed in June — expired without an agreement to reopen the Strait of Hormuz, lifting Brent +2.7% to 90.87$; also that day, US federal debt crossed the 40 trillion dollar threshold, months earlier than estimates had suggested.
More important than the US figure, the break was global and simultaneous: Japan’s 10-year government bond yield reached 2.945% — the highest since September 1996; Germany’s exceeded 3.25% — the highest since March 2011; and France’s reached 4.10% — the highest since June 2009. The UK 30-year government bond yield, at 5.85%, broke only a recent rather than historical ceiling — its highest level only since May 2026 — an exception we identify rather than bury.
The diagnosis is a direct extension of what we observed a week ago in the yield curve research: the 2-year yield barely moved — from 4.15% last Thursday to 4.19% on Monday — while the 30-year yield jumped ten basis points (Basis Points) in two sessions, widening the spread between the two maturities from 99 basis points on 31 July to 112 points at Monday’s close. This is not a repricing of the Federal Reserve path — the probability of a rate rise in September remains near 30% — but a repricing of governments’ own borrowing costs: the real yield (Real Yield) and market inflation compensation (Breakeven Inflation) rose together, with the latter reaching 2.30% — its highest reading in the past month. Our positioning data show that the break occurred while the investor base was positioned long: asset managers (Asset Managers) held a net long position (Net Long Position) of around 2.55 million contracts in 10-year maturities alone a week before the sell-off.
Each panel has an independent scale — values are 17–18 August closes, and the dashed line marks the prior high and its date
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