Nearly a hundred billion dollars of "ammunition" only bought two weeks of respite? The rare intervention by the US and Japan can't stop the yen from approaching the 160 threshold.

Less than two weeks since the historic joint intervention by the U.S. and Japan, the yen has given back about half of its gains. The fundamental reason lies in the macroeconomic forces that previously pressured the yen to decades-low levels; after a brief setback, these forces have again reasserted control over the currency's trajectory. Currently, the yen is trading at above 159 yen to 1 U.S. dollar. Previously, the yen had fallen below the 163 level against the dollar, but after the intervention, it temporarily rose to 155. Nearly a hundred billion dollars in ammunition has only resulted in a brief rebound? The Japanese Ministry of Finance confirmed that Japan coordinated with the United States to implement foreign exchange market intervention on July 31, U.S. Eastern Time. Market institutions estimate that Japan individually injected about 54 billion dollars on July 30 and another 34 billion on July 31, totaling approximately 88 billion dollars over two days, while the scale of the U.S. plan was between 5 to 10 billion dollars. The New York Federal Reserve, representing the U.S. Treasury, purchased yen, marking the first time the U.S. has entered the yen-buying market since the 1998 Asia Financial Crisis. However, it seems that almost a hundred billion dollars in ammunition has only yielded a fleeting rebound. "The intervention action startled the market but did not prevent financial rules from taking effectcapital always flows to the highest returning direction... As long as Japan's funding costs remain lower than overseas returns, arbitrage trading will reoccur," stated Jesper Koll, Chief Expert Director at Monex Group. The core issue lies in the return rate disparity between the U.S. and Japan. Japan's borrowing costs remain significantly lower than those in the U.S. and other markets, prompting investors to borrow low-cost yen and redirect their investments to higher-yielding assetsthis is the classic arbitrage trading operation. Moreover, the macro environment has become more challenging: rising U.S. Treasury yields combined with higher oil prices pose a unique challenge for Japan, which is highly dependent on energy imports. These macro factors again support the dollar. However, some believe that while the intervention measures have not eliminated the potential yield advantage supporting the dollar, they have successfully reduced excessive speculative behavior and increased the risks of shorting the yen. "This intervention has successfully reshaped market psychology and demonstrated the unusually close policy coordination between the U.S. and Japan, even though it has not eliminated the yield advantage supporting the dollar," said Masahiko Loo, Senior Fixed Income and Currency Strategist at State Street Global Advisors. The gap in interest rates remains significant: the benchmark 10-year U.S. Treasury yield is at 4.686%, while Japan's 10-year government bond yield is only 2.846%, meaning investors have significant motivation to hold U.S. Treasuries. "A more appropriate understanding is that the intervention has succeeded in curbing speculation, but it has yet to prove effective in changing the fundamentals," Loo added. This has shifted market attention to the Bank of Japanits next monetary policy meeting is scheduled for September. Market pricing shows a roughly 50%-60% probability that the Bank of Japan will raise interest rates by 25 basis points during its meeting on September 17-18. Monexs Koll pointed out that the larger shock for investors is not the intervention itself, but the Bank of Japan's indecision regarding more aggressive tightening of policy. This raises the question: Are concerns about the banking system or Japan's massive public debt burden constraining decision-makers? As long as Japanese interest rates do not rise and U.S. Treasury yields do not fall, the motivation for investors to allocate funds overseas remains. John Wood, Chief Investment Officer for Asia at Lombard Odier, expressed that the latest intervention measures may only produce "limited time effects," suggesting that the Bank of Japan might need at least two more interest rate hikes to curb the weakening of the yen. Beneath the appearance of exchange rates lies structural economic challenges. Some argue that the interest rate gap may only be part of the reason. Credit Agricole pointed out that a deeper issue is the "asymmetry of investment strength" between the two major economies, the U.S. and Japan. The U.S. continues to attract capital inflows with significant investments in fields like artificial intelligence, while Prime Minister Fumio Kishida's public and private investment plans in Japan have not yet fully materialized. "To correct the yen's weakness, what is needed is not an interest rate hike, but the expansion of investment," the bank stated. This implies that for the yen to achieve a sustainable recovery, Japanese assets must ultimately become more attractive, encouraging domestic savings to remain local rather than chase after overseas returns. Currently, rather than reversing yen depreciation, the intervention measures can be seen as a safeguard against accelerating yen depreciation. State Street's Loo noted that the 160 level has become a "political red line," meaning if the exchange rate were to rapidly surpass this level again, it could trigger authorities to re-enter the market. "I do not rule out the possibility of further intervention, especially if exchange rate movements become rapid or disorderly," he stated. "However, ultimately, intervention can only buy time; the key factor remains the policy normalization by the Bank of Japan, which may begin as early as September." The U.S. and Japan are also strengthening their deterrence, with both sides emphasizing the Federal Reserve's repo facility for foreign and international monetary authorities, which can provide dollar liquidity collateralized by U.S. Treasuries, thereby reducing the necessity for Japan to sell its Treasury holdings to intervene in the foreign exchange market. U.S. Treasury Secretary Janet Yellen has expressed support for expanding this liquidity support mechanism. While this move may raise the costs of shorting the yen, it does not eliminate the fundamental logic of arbitrage trading. "Its easy to scare the market, but getting the market to follow you requires changing the incentive structures and building trust," Koll summarized. Interventions may buy time, but ultimately, it will be Japan's own economic structural transformation and credible policy pathways that will stabilize the yen.