Long-Term Yields Surge to Two-Decade Highs
Government bond markets endured a punishing summer with long-term yields climbing to levels not seen in nearly two decades, fueled by inflation fears, mounting public debt, and competition for investor demand. Between late June and mid-September, the US 10-year yield rose by more than half a percentage point to reach 5%, marking its highest point since summer 2007 and surpassing the October 2023 peak of 4.98%. The US 30-year yield climbed to 5.37%, a level last seen in June 2007.
By September 25, the US Treasury’s own daily curve put the 10-year at 5.17% and the 30-year at 5.49%, their highest levels since July 2007 and June 2004 respectively. This trend was not confined to the United States; the 10-year Bund gained over 60 basis points to 3.54%, its highest since June 2009, suggesting common global roots for the pressures. The UK 10-year gilt hovered around 5.37%, its highest rate since 2008, and the Japan 10-year hit 3.073%, the highest since 1996.
Geopolitical Shocks and Inflation Expectations
Geopolitics played a significant role in rising yields, citing the collapse of the agreement between Washington and Tehran, Houthi attacks in the Red Sea, and renewed military operations in Iran from early July as factors pushing Brent crude toward $100 per barrel and European natural gas above €80 per megawatt-hour. Markets revised inflation expectations upwards, with Eurozone inflation swap rates exceeding 3% for one- and two-year maturities.
The term premium rose most sharply between July and August, acting as a proxy for doubts about inflation and long-term real growth. Mortgage rates exceeded the 7% threshold last week following a widely expected hike by the Federal Reserve, further illustrating the transmission of these macroeconomic pressures to consumers.
Structural Debt Burdens and AI Issuance
The structural backdrop for this yield environment is defined by massive sovereign debt loads. US federal debt held by the public reached $31.7tn in Q2-26, equal to 97.5% of GDP, with gross interest payments absorbing roughly 21% of US government tax revenue, almost double the share at the start of 2022. Europe faces similar strains, with the Eurozone debt-to-GDP ratio just below 90% in Q1-26, and Italy and France standing at 138.6% and 117.6% respectively.
A newer factor is the surge in long-dated issuance by AI companies; Amazon, Oracle, Alphabet, and Meta issued a combined $109bn in bonds in 2025 and $250bn since the start of 2026, potentially drawing away marginal demand from maturing Treasuries. AI related issuers are already paying an elevated premium as high as 115 basis points compared to other investment-grade borrowers.
Market Mechanics and Foreign Demand
The effect of US Treasury buybacks proved short-lived; yields climbed even after the first auction on 9 September despite the operation being increased to $6bn, with $5.2bn allocated. There are signs of reduced foreign Treasury demand, with indirect bidders falling from 66% in August to 57.8% in last week’s auctions on the two-year and 60.8% to 57.2% on the seven-year.
Risks to Global Stability
All three of the OECD, IMF, and IIF warned this week that a sudden and steep re-pricing of global liabilities risks a cascade of economic and political crises. Oracle declared force majeure on its Project Jupiter data center in New Mexico citing delays in sourcing power for the project, as debt repricing drives up borrowing costs for hyperscalers.
Yields are likely to stay elevated as structural forces behind their rise remain firmly in place, despite long-term rates easing slightly after the Federal Reserve’s FOMC meeting on 15 and 16 September.