The yen’s rebound after rare joint action by U.S. and Japanese authorities is already losing momentum, placing renewed pressure on the Bank of Japan to show whether it can support the currency through policy rather than intervention alone. The yen weakened to as much as 159.39 per dollar on Aug. 12 before ending roughly unchanged, wiping out about half of the gains made after the authorities acted in late July.
The move brings the currency back within sight of 160 per dollar, a level closely watched by traders after previous bouts of volatility drew official responses. Japan’s Ministry of Finance has repeatedly treated rapid, one-sided currency moves as a concern, while the United States has generally been reluctant to participate directly in foreign-exchange operations.
On July 31, the U.S. Treasury joined yen-support operations for the first time in nearly three decades, with the New York Federal Reserve carrying out transactions through dealers. The operation involved selling euros and buying yen, according to the account of the intervention. The yen moved from about 163 to 155 in the immediate aftermath.
That sharp response demonstrated that coordinated action can shift exchange rates quickly, particularly when markets are positioned for further yen losses. Yet the subsequent slide also shows the limits of intervention when the underlying return advantage remains heavily tilted toward dollar assets.
Yield gap continues to favor the dollar
The 10-year U.S. Treasury yield stood at 4.686%, compared with 2.846% for the equivalent Japanese government bond, leaving a gap of more than 180 basis points. That spread remains large enough to preserve the appeal of the yen carry trade, in which traders borrow cheaply in yen and place funds in higher-yielding currencies or assets.
Carry trades have long amplified the yen’s sensitivity to interest-rate differentials. A trader able to borrow in a currency with relatively low rates can earn a higher nominal return elsewhere, provided exchange-rate moves do not erase that income. The strategy becomes less attractive when the yen strengthens quickly, since repaying yen-denominated borrowing becomes more expensive.
The recent exchange-rate action suggests that intervention has made traders more cautious around 160, without fully removing the incentive created by the yield gap. Rapid moves toward that level may raise the risk of another official response, but a stable currency reversal would likely require either lower U.S. yields, higher Japanese yields, or both.
Higher international oil prices have added another challenge for Japan. As a major energy importer, Japan faces a larger import bill when oil rises, and a weaker yen increases the local-currency cost of dollar-priced energy purchases. The same environment can reinforce dollar demand, particularly if higher energy costs feed expectations that U.S. inflation and interest rates will remain elevated.
September Bank of Japan meeting moves into focus
Attention is now turning to the Bank of Japan’s September policy meeting. The central bank has been moving gradually away from its long period of exceptionally loose monetary policy, but the pace of normalization has remained modest compared with the rate levels maintained in the United States.
John Wood of Lombard Odier said the Bank of Japan may need at least two additional rate increases to halt persistent yen weakness. His assessment reflects the scale of the remaining gap between Japanese and U.S. borrowing costs rather than the effect of a single currency operation.
Jesper Koll of Monex Group has also linked the market’s focus to the pace of Japanese monetary tightening. In his view, the issue extends beyond whether authorities intervene in foreign exchange markets: traders are testing how far the Bank of Japan can raise rates while managing the consequences for domestic banks and Japan’s large government debt burden.
Those constraints help explain why Japanese policymakers face a more difficult trade-off than a simple choice between a stronger yen and higher rates. Faster tightening could support the currency by raising domestic yields. It could also increase financing costs across an economy where public debt is substantial and parts of the financial system have operated for years with low interest rates.
Dollar liquidity facility gives Japan another tool
Japan also has access to the Federal Reserve’s Foreign and International Monetary Authorities repo facility, commonly known as FIMA. The facility allows foreign monetary authorities to obtain dollar liquidity by placing U.S. Treasuries as collateral.
For Japan, that mechanism could reduce the need to sell Treasury holdings outright when assembling dollars for currency-market operations. A direct sale of Treasuries can add pressure to bond markets; using the repo facility instead allows authorities to raise temporary dollar liquidity while retaining ownership of the securities.
The facility does not alter the yield differential that encourages yen-funded trades, but it gives Japanese authorities a more flexible operational option if intervention becomes necessary again. That matters during periods of market stress, when selling large holdings of government bonds can have effects beyond the currency market.
Amundi has pointed to a longer-running structural issue behind the yen’s weakness: Japanese savings continue to find stronger return opportunities abroad. The firm described an “investment capacity asymmetry” between the United States and Japan, citing sustained U.S. spending in areas such as artificial intelligence alongside a slower rollout of Japanese public-private investment plans under Prime Minister Sanae Takaichi.
A firmer yen would therefore depend on more than official intervention or a near-term rate increase. Higher domestic returns and stronger investment opportunities could keep more Japanese capital at home, reducing the persistent incentive to exchange yen for foreign assets. Until that changes, the approach to 160 is likely to remain a test of both the Bank of Japan’s policy resolve and the authorities’ willingness to act again.
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