War, AI investment, and debt hit bond markets all at once
📌 Post Summary
📌 Post Summary
Government bond yields across the US, UK, Germany, and Japan have simultaneously hit multi-year to multi-decade highs. The US 10-year yield reached 4.81%, its highest since January 2025, while the 30-year climbed to 5.27%, approaching pre-2007 financial crisis levels. The UK 30-year hit its highest since 1998, Germany’s 10-year its highest since 2011, and Japan’s 10-year entered the 3% range for the first time in 30 years. The trigger: renewed US-Iran conflict driving oil prices higher, a surge in AI infrastructure corporate bond issuance by Big Tech, and mounting government fiscal deficits — three forces converging at once. South Korea’s KOSPI also swung sharply during today’s session as a result.
Sell orders have been pouring into global bond markets all at once over the past several days. Long-term government bond yields in the US, UK, Germany, Japan, and beyond have simultaneously spiked to multi-year or multi-decade highs, putting governments, companies, and households on alert over rising borrowing costs. Here’s where this “global rate spasm” started, what factors are converging behind it, and how it’s rippling into the domestic market.
① What’s happening — multi-year to multi-decade highs
The US 10-year Treasury yield rose to 4.796% on September 1, its highest level since mid-January 2025, then climbed further to 4.81% on September 2. The 30-year yield, which serves as the benchmark for mortgage rates, rose to 5.272%, edging close to levels last seen just before the 2007 global financial crisis. It’s not just the US. The UK 30-year gilt yield climbed to 5.919% intraday, its highest since 1998, while Germany’s 10-year Bund yield hit 3.339%, its highest since 2011. In Japan, the 10-year JGB yield entered the 3% range for the first time in 30 years — widely read as a signal marking the end of the ultra-low-rate era.
② The trigger: US-Iran conflict reignites → oil spikes → inflation fears return
The direct trigger behind this rate spasm is the military conflict between the US and Iran that resumed on August 30. A tanker was struck near the Strait of Hormuz, adding to fears of disruption to oil supply chains, and Brent crude futures, the international benchmark, topped $95 a barrel on September 1. The oil price spike reignited inflation concerns that had seemed to be fading, feeding into expectations that central banks’ tightening stance could stay tighter and last longer than previously expected — a shift that rattled bond markets broadly.
③ Structural factor: AI infrastructure bond issuance competing with government debt for capital
The geopolitical trigger alone doesn’t fully explain this rate spasm. Underlying it is a much more structural factor: massive corporate bond issuance by Big Tech to fund the AI investment boom. The five major “hyperscalers” — Amazon, Alphabet, Microsoft, Meta, and Oracle — are estimated to issue roughly $250 billion in corporate bonds this year, about double last year’s level. This wave of fundraising for data centers and chip investment is landing at the same time governments are issuing government bonds to cover their own fiscal deficits, effectively pitting governments and Big Tech against each other for the same pool of capital. When bond supply surges all at once, investors demand higher yields to absorb it — adding further upward pressure on long-term rates.
④ Mounting fiscal deficits — US national debt approaching $40 trillion
Accumulated fiscal deficits across countries are also adding to the upward pressure on rates. US government debt is approaching $40 trillion, having grown by roughly $5 trillion in just two years. Normally, when central banks tighten policy, slowing growth and inflation also ease the upward pressure on long-term rates — but analysts say the situation has changed as governments simultaneously expand fiscal spending. As deficits grow, so does the volume of government bond issuance, and the “term premium” long-term bond investors demand to absorb that supply rises in turn, pushing long-term rates even higher.
⑤ Domestic spillover — KOSPI’s rollercoaster session today
This ripple effect reached Korean markets directly. The KOSPI opened up 1.33% at 6,650.33 on September 3, but tumbled 1.88% intraday to 6,439.49 under the shock from surging oil prices and rates. It then reversed near the close, driven largely by share buybacks from “other corporations,” to finish up 0.26% at 6,579.48 versus the prior session. It was an unusual day in which the index closed higher even as individuals, foreign investors, and institutions were all net sellers (individuals sold ₩955.1 billion, foreigners ₩419.3 billion, institutions ₩215.2 billion). The rise in Treasury yields is also feeding directly into mortgage rates — the US mortgage rate, tied to the 30-year yield, is approaching pre-2007 financial crisis levels, and corporate bond issuance costs are climbing in tandem.
⑥ Analyst views — monetary policy being repriced, but opinions diverge
Market analysts aren’t converging on a single diagnosis. Andrew Lilley, chief rates strategist at Australia’s Barrenjoey, said the bond sell-off stems from the market repricing the US Federal Reserve’s monetary policy path, and argued the Fed is likely to deliver at least three consecutive rate hikes starting with the September FOMC meeting. Capital.com market analyst Daniela Hathorn, by contrast, said slowing growth, cooling inflation, and an eventually more dovish Fed stance could actually pull short-term rates lower. She added, however, that long-term rates remain exposed to pressure from heavy government bond supply, large fiscal deficits, AI-related corporate bond issuance, and energy and inflation uncertainty — suggesting short- and long-term rates could diverge going forward.
📌 Good to Know
- Rising long-term rates feed directly into mortgage rates and corporate bond issuance costs, so it’s worth tracking rate trends if you have borrowing or investment plans in the pipeline.
- Since short- and long-term rates may move in different directions in this environment, diversifying maturities is worth considering for bond investments.
- Middle East geopolitical risk directly affects the path of oil prices and inflation, so it’s worth checking related news flow regularly.
- Korean equities are highly sensitive to swings in overseas rates and oil prices, so risk management for near-term volatility is important.
A war-driven oil shock, a corporate bond issuance rush fueled by the AI investment boom, and accumulated fiscal deficits — this global bond yield spasm is a complex event that can’t be pinned on any single cause. As long as the US-Iran situation remains unresolved, and as long as Big Tech’s AI investment race continues, upward pressure on long-term rates is likely to persist for the time being. Policy decisions from major central banks, starting with the September FOMC, are likely to mark the next turning point.
Sources
- Money Today (mt.co.kr) — “Global Bond Yield Tsunami Rattles Governments, Businesses, and Households”
- Money Today (mt.co.kr) — “Why the Global Bond Yield Spasm? A Triple Wave of Inflation, Debt, and AI”
- Money Today (mt.co.kr) — “Global Rates Hit Multi-Year Highs Simultaneously, Crushing Debt-Laden Governments, Businesses, and Households”
- Herald Corp (heraldcorp.com) — “US Treasuries Compete With AI Corporate Bonds for Capital — Big Tech’s Debt Binge Sparks Long-Term Rate Alarm”
- Financial News (fnnews.com) — “‘I Thought It Was Falling’ — KOSPI Ends Higher on Buying From Other Corporations”
- Gukje News (gukjenews.com) — “KOSPI Closes Up 0.26% at 6,579.48, KOSDAQ Falls 1.71%”