'Dear God': Japan's borrowing costs hit 30-year high

Japan's 10-year government bond yield reached 3% on Tuesday, September 1, 2026, marking its most expensive rate since September 1996, according to Protos. The yield has increased 2,900% in less than five years, rising from just 0.1% in early 2022, Protos reports. The broader yield curve shows Japan paying 1.81% to borrow for two years, 2.26% for five years, 3.8% for 20 years, and 4.18% for 30 years. The 40-year JGB (Japanese Government Bond) duration trades below a multi-decade record at 4.28%, though it set a recent record of 4.4% in May, per Protos. Techniquely, 30-year bonds traded higher in May 2026, and formal 30-year JGB history extends only to 1999, Protos notes, so the current 4.18% yield is a multi-decade record rather than an all-time high across full historical records. Tuesday's 10-year JGB auction attracted more than three bids per bond, keeping bidding in line with the annual average despite the elevated yield, Protos reports. The market appetite suggests bond investors are absorbing higher rates, though they signal distress elsewhere. The Bank of Japan raised its policy rate to 1% in June, the highest in 31 years, and , according to Protos. The central bank's July outlook projects core consumer prices rising sharply above its target, with CPI likely to accelerate to a level clearly above 2% from the second half of fiscal 2026, Protos reports. Yen weakness has accompanied the rate-driven yield surge. On July 31, with the yen near a 40-year low relative to the US dollar, the US and Japanese governments bought yen together for the first time since 1998, per Protos. Tokyo's finance ministry said the action countered excessive volatility and disorderly movements in the yen in recent months. Japan, the largest foreign holder of US debt, also tapped a Federal Reserve facility to borrow dollars against its $1.1 trillion US Treasury stockpile, Protos reports. The intervention did not hold. Within eleven days, the yen resumed weakness relative to the dollar, trading back near 160 per dollar this week, Protos reports, indicating that coordinated action proved insufficient to stabilize the currency. Debt servicing is set to cost the Japanese government a record 36.6 trillion yen, or approximately $230 billion, next year, up 17% in one year, according to Protos. That acceleration reflects both higher yields on new issuance and the government's maturing debt obligations rolling into a higher-rate environment.