In May, the yield on ten-year Japanese government bonds hit 2.8%, its highest level in nearly three decades. For a market that spent a period anchored near zero, this wasn’t a technical correction — it was a tremor that echoed across the Pacific: as Japanese yields rose, US Treasury yields moved with them.
This is not new. In January, when an earlier JGB selloff hit the US Treasury market, Treasury Secretary Scott Bessent said he had been in contact with his Japanese counterpart and expected Tokyo to “start saying things that would calm the market.”
The Japanese government bond market is no longer a domestic affair. It has become a load-bearing wall of the global financial system – and right now, that wall is being asked to do something it cannot: save the yen.
For most currencies, the exchange rate tracks short-term interest rate differentials and analysts watch the two-year yield gap. Japan is an exception. After the BOJ set policy rates at the zero lower bound and returned to yield curve control, long-term yields became the operating channel – which is why the ten-year US-Japan spread has tracked USD/JPY more closely than the two-year spread.
Suppressed JGB yields prompted Japanese life insurers and pension funds to target returns abroad, and these flows became a structural engine of yen weakness; normalization is intended to run that engine in reverse. For a while, it seemed to work.
Since the BOJ began reducing its 500 trillion yen balance sheet in the second half of 2024, the yen’s free fall has given way to a slower decline — evidence the bipartisan camp cited. But moderation is no change: the yen has since passed 162 to the dollar, a four-decade low, with the Finance Ministry intervening almost daily to little effect.
Quantitative tightening (QT) slowed the devaluation but did not change destination because the pressure did not originate from the differential at all.
It is not a bilateral problem
Draw the triangle however you will – the BOJ, Tokyo’s fiscal authorities and a Washington that wants a stronger yen and lower Treasury yields; or Japan, the United States and China. The bodies matter less than the common ground: no two-sided cut of this problem captures it.
BOJ tightens to protect yen. But with debt nearing 260% of GDP and Prime Minister Sanae Takaichi financing a 21 trillion yen stimulus package with deficit bonds, any rise in yields raises debt service costs.
Japan is the largest foreign holder of US Treasuries. When BOJ tightening raises JGB yields, that flow reverses on the margin and Japanese capital goes home—the channel that drove the JGB selloff to the Treasury market and the reason Bessent, whose deepest concern is the US ten-year, can’t just enjoy a tough BOJ.
Bessent, who visited Japan in May, has repeatedly suggested faster BOJ rate hikes are the cure for the weak yen. But get the BOJ to tighten aggressively and it gets the very thing it most wants to avoid: escalating US ten-year Treasury yields. His real choice is not between a strong yen and a weak one, but between a weaker yen and higher long US rates.
This points to a compromise already taking shape: stop QT in fiscal 2027 while continuing to grow cautiously. The appeal is that the levers hit different ends of the curve. QT works for the long haul—where the BOJ’s withdrawal has already pushed 30-year yields toward 3.6%—so stopping it saves fiscal arithmetic and, through the savings channel, US Treasuries.
The rate hikes work on the front end, maintaining the appearance of protecting the yen while giving Takaichi its fiscal room.
Why compromise fails
The problem is that the compromise rests on a lever with no travel left. With the end of QT, first-tier hikes become the yen’s only hedge – and inflation data says they can’t be pushed away. Headline inflation was 1.5% in May and core CPI remained at 1.4%, below target for the fourth consecutive month.
But the inflation cap is only a short-term constraint. Even if inflation were to return to 3% tomorrow, giving the BOJ room to raise rates above 2%, it would not be enough. The rate difference is a flow; China’s accumulated real depreciation since 2022 is a stock, and no credible increase from the front clears a gap that has been building for years.
The leverage isn’t just limited – it’s the wrong instrument for the force it’s being asked to compensate for. The compromise may stay in the JGB market for a while; can’t change where you are going. With the intervention unable to hold the line, the path of least resistance for USD/JPY is still higher.
That force, as I argued in this column before, is China. Years of Chinese deflation have given exporters a cumulative price advantage over Japanese competitors approaching 25-30% in overlapping industrial sectors.
Because Beijing manages the yuan against the dollar and won’t let it appreciate to reflect this advantage, the adjustment has shifted to the currencies of China’s closest competitors – and the yen absorbs most of it.
This is China Shock 2.0: a real price gap of 25 to 30 points against which a rate move of 50 points is not a counterweight but a rounding error.
The missing variable
Tokyo is solving an external structural problem with domestic monetary means; Washington is trying to strengthen the yen without destabilizing its own treasury market. Neither can overcome the dominant force acting on the Japanese currency. The BOJ can influence the timing of the adjustment and its volatility, but it can no longer determine its direction.
And the direction is set in Beijing. The yen’s trajectory depends on whether China’s deflationary spiral deepens or reverses, and China’s own policy choices dictate that direction. As long as Beijing relies on supply and suppresses domestic demand, deflationary compounds and the yen continue to absorb the pressure.
Genuine reflation would ease it – but Japan’s lost decades are a cautionary tale: once entrenched, deflation is notoriously difficult to reverse, even with zero rates, quantitative easing and years of effort. There is little reason to expect China to escape quickly what Japan could not escape for a generation.
This is the real three-body problem of Japan’s bond market – and its solution lies not in the BOJ’s balance sheet or Bessent’s calls, but in a rebalancing of the world’s second-largest economy that is, to say the least, not imminent.
Steven Linsley is an independent macroeconomic commentator.
