Sony Financial: JGB Yields Face 35-Basis-Point Upside Risk Amid Fiscal Pressures and BOJ Hawkishness
Long-term Japanese government bond (JGB) yields are on a gradual upward trajectory, driven by rising oil prices and a sustained hawkish posture from the Bank of Japan (BOJ). While current yield levels align with broader market expectations, a renewed focus on government spending could push long-term rates higher by as much as 15 to 35 basis points, according to a new research note from Sony Financial Group.
In the firm’s latest Global Economy & Interest Rate Watch, Senior Economist Takayuki Miyajima notes that Japan's 10-year JGB yield recently breached the 2.5% threshold in early May. Following the BOJ’s decision to hold rates steady at its April meeting, short-term rates dipped slightly, leading to a notable widening of the short-to-long-term yield spread.
However, Miyajima points out that the spread between super-long and long-term yields remains relatively contained, suggesting that the bond market is not currently pricing in severe sovereign fiscal risks—though that could soon change.
The Road to a June Hike
Sony Financial is maintaining its forecast for the BOJ's policy trajectory, anticipating the next rate hike in June, followed by a pace of one hike every six months.
Despite the BOJ holding fire in April, the central bank's medium-term signaling remains hawkish. Miyajima notes that the hurdle for a June hike is "by no means low." However, complicating the BOJ’s path are potential downside risks to the broader economy, including declining industrial production in the chemical and petroleum sectors, and the lingering threat of supply chain disruptions in the Strait of Hormuz.
Given the difficulty the government would face in justifying a rate hike amid looming recessionary fears, Miyajima argues that the primary catalyst forcing the BOJ's hand in June will likely be persistent weakness in the yen.
Yield Cap and Fiscal Risks
Are current yield levels overextended? According to the report, a 10-year yield above 2.5% is justified. Based on the relationship between overnight indexed swaps (OIS) and long-term rates, the market is currently pricing in a terminal rate of 2.0%. This translates to an estimated fair-value long-term yield of roughly 2.6%.
The true upside risk to Japanese yields, Miyajima warns, lies in fiscal policy. Short-term risks of fiscal deterioration cannot be ignored, particularly given the high likelihood that the government will extend or expand subsidies for gasoline and utilities. Furthermore, debates over proposed grocery tax cuts—which could reduce tax revenues by 5 trillion yen annually—and increased fiscal spending for the government's June economic policy guidelines are expected to intensify.
Historical data suggests that when fiscal risks take center stage—such as during the pre-election spending debates in mid-2025 or the tax-cut discussions in early 2026—long-term yields tend to overshoot their trend lines.
Should similar fiscal concerns materialize in the coming months, Sony Financial estimates an initial 15-basis-point upside risk to long-term yields. In a more severe scenario of fiscal deterioration, this premium could expand to 19 to 35 basis points. Meanwhile, super-long (40-year) JGB yields could face an upward shock of 30 to 50 basis points.
Moving forward, bond markets will need to maintain a dual focus: tracking the geopolitical developments in the Middle East, while closely monitoring whether Tokyo's fiscal debates will ultimately unmoor domestic interest rates.
Data Annex: Sony Financial Group's Interest Rate Projections (As of May 2026)
The report outlines the following baseline forecasts for Japanese interest rates
and inflation:
Policy Rate & JGB Yields (%)
- Policy Rate: Rising from 1.00% (Q2/Q3 2026) to 1.25% (Q4 2026/Q1 2027)
- 5-Year JGB: Rising from 1.90% (Q2 2026) to 1.96% (Q1 2027)
- 10-Year JGB: Rising from 2.50% (Q2 2026) to 2.55% (Q1 2027)
- 20-Year JGB: Stabilizing around 3.30% to 3.31% through Q1 2027
- 40-Year JGB: Peaking at 3.93% (Q1 2026), tapering slightly to 3.87% by
Q1 2027
Inflation (% YoY)
- Core CPI (ex-fresh food): Trending at 2.37% (Q2 2026), expected to end
Q1 2027 at 2.34% - Core-Core CPI (ex-fresh food & energy): Trending at 2.13% (Q2 2026), ending
Q1 2027 at 2.20%
Norbert Gehrke
