MediumIV Macro Policy & Sovereign Debt3 September 2026, Thursday · 12:35 TRT (UTC+3)
Japan's 30-year government bond auction draws an average yield of 4.079%
Demand for ultra-long yen borrowing held up, but yields are in record territory ahead of the central bank's 18 September decision.
According to results announced by Japan's Ministry of Finance on 3 September, the 30-year government bond auction with a 4.0% coupon drew an average yield of 4.079% and a highest accepted yield of 4.100%. The bid-to-cover ratio was about 3.79 and the amount sold 599.6 billion yen. Japan's 30-year yield stood at 4.12% on 16 September, with a September record of 4.21%.
According to an ING assessment dated 11 September, the Bank of Japan is expected to raise its policy rate from 1.00% to 1.25% on 18 September, which would be the highest level since April 1995. Rising yen-denominated long-term yields could strengthen the tendency of Japanese institutional investors to repatriate overseas assets and put upward pressure on global long-term interest rates.
Talay assessment
Bottom line
An average yield of 4.079% and a bid-to-cover ratio of about 3.79 show that demand for ultra-extended yen debt persists, but only at yields in record territory. If the 18 September hike expected by ING takes the policy rate to its highest since April 1995, Japanese institutional investors' tendency to repatriate overseas assets strengthens, putting upward pressure on global extended-maturity rates. The most likely course is for the hike to go ahead and Japanese yields to stay in an elevated band.
Likely effects
- Global extended-maturity ratesNegative1–6 months
As domestic yields become more attractive, Japanese institutional investors cutting overseas bond holdings put upward pressure on US and European extended-maturity yields; global borrowing costs rise.
- Japan's public financesNegative1–6 months
Ultra-extended yields in record territory gradually raise interest costs for heavily indebted Japan; fiscal space narrows.
- Emerging market financingNegative1–6 months
Japanese capital repatriation and rising global yields could weaken portfolio flows to emerging economies that need external financing, such as Türkiye, and raise their borrowing costs.
Possibilities, ranked
- 1Hike and yields in an elevated band60%
The Bank of Japan raises the rate to 1.25% on 18 September; the 30-year yield fluctuates in the 4.12–4.21% band.
Watch: The 18 September policy decision and whether the 30-year yield tests its 4.21% record
- 2Hike postponed20%
Citing market volatility or growth concerns the bank keeps the rate at 1.00%; the yen weakens and extended-maturity yields stay high on inflation concerns.
Watch: The rate left unchanged at the 18 September decision and a sharp depreciation of the yen
- 3New record and global sell-off20%
After the hike yen yields break above the 4.21% record; repatriation accelerates and global extended-maturity yields rise simultaneously.
Watch: The 30-year yield exceeding 4.21% and a marked drop in the bid-to-cover ratio at the next ultra-extended auction
Probabilities are calibrated judgement based on the sources, not measurement, and are revised as new information arrives. Not investment advice.
Market reaction
Indicators affected
- Japan 30Y▲ 4.12%
Historical context