Japan’s government bond market, long viewed as a pillar of global financial stability, is showing signs of strain and investors around the world are paying close attention.

In mid-January, yields on Japan’s 40-year government bonds surged above 4% for the first time in more than three decades, marking a dramatic shift for a market once defined by ultra-low rates and minimal volatility. The move reflects a combination of structural and political changes that are reshaping investor expectations.

A key factor is the gradual retreat of the Bank of Japan from its long-standing role as the dominant buyer of government debt. After decades of aggressive bond purchases aimed at combating deflation, the BOJ has begun scaling back its holdings as inflation finally takes hold. With the central bank stepping aside, demand from other investors has struggled to fill the gap, leading to weaker auctions and heightened price swings.

Fiscal policy has added to market unease. Prime Minister Sanae Takaichi’s government recently approved a ¥21.3 trillion stimulus package – the largest since the pandemic – alongside proposals to suspend the country’s food sales tax. Investors fear these measures will require increased bond issuance at a time when demand is already fragile. Neither the ruling coalition nor the opposition has offered clear funding plans, raising broader concerns about fiscal discipline.

While higher yields have attracted foreign investors seeking improved returns, domestic institutions remain cautious. Japanese life insurers, major holders of long-dated bonds, have already reported significant unrealized losses as yields rise. Continued volatility risks further balance-sheet pressure across the financial sector.

The implications extend beyond Japan. Rising yields in the world’s third-largest bond market could spill over globally, particularly as governments elsewhere grapple with persistent deficits and inflation risks. US and European bond markets have already faced upward pressure following renewed trade tensions and shifting expectations around central bank rate cuts.

Both Japanese policymakers and global officials are monitoring developments closely. The BOJ has signaled it is prepared to adjust bond purchases if volatility threatens market stability, while the government has shifted issuance toward shorter-term debt to limit pressure on long-term yields.

Still, with inflation re-emerging and fiscal expansion firmly on the agenda, Japan’s bond market may no longer serve as the global anchor it once was – marking a significant turning point for investors worldwide.