Can US-Japan Joint Intervention Save the Yen? 160 Barrier Under Threat, Depreciation Drivers May Extend Beyond Interest Rates

Less than two weeks after the Japanese government and the United States jointly intervened in the foreign exchange market, the yen has already given back about half of its appreciation, once again approaching the 160 level. This rare US-Japan coordinated action successfully deterred some speculative funds betting on yen depreciation, but it has not yet changed the fundamentals driving the yen’s long-term weakness.

Jesper Koll, Executive Director at Monex Group, pointed out that while the intervention did instill fear in the market, "as long as Japan’s funding costs remain lower than overseas investment returns, capital will flow back into higher-yielding markets, and yen carry trades will revive."

The real challenge lies in Japan’s borrowing costs, which remain far below those in the United States and other major markets. This allows investors to borrow yen at low cost and invest the funds in dollar-denominated assets or other high-yield markets—forming the classic "yen carry trade." As long as the returns from this trade remain attractive, one-off currency interventions will struggle to reverse the yen’s long-term weakness.

According to CNBC analysis, recent rises in US Treasury yields, coupled with persistently high oil prices, are adding further pressure on the yen. For Japan, which relies heavily on energy imports, high oil prices worsen its terms of trade and further weaken the yen. Rising US Treasury yields also enhance the appeal of dollar-denominated assets.

Masahiko Loo, Senior Fixed Income and Foreign Exchange Strategist at State Street Global Advisors, stated that the intervention successfully reset market psychology and demonstrated rare US-Japan policy coordination. However, "it has not eliminated the interest rate advantage supporting the dollar."

The US-Japan interest rate differential remains substantial: the 10-year US Treasury yield stands at 4.686%, while the 10-year Japanese government bond yield is 2.846%, a gap of approximately 1.84 percentage points. Investors still earn significantly higher returns by holding US bonds.

For this reason, this intervention is better interpreted as "successfully slowing speculation" rather than having fundamentally reversed yen depreciation.

The key to halting yen depreciation lies with the Bank of Japan

This has refocused market attention on the Bank of Japan, with the next monetary policy meeting scheduled for September.

Koll believes the real surprise is not the government’s intervention, but the Bank of Japan’s reluctance to tighten monetary policy more aggressively. This raises market doubts: are concerns over financial system stability and Japan’s massive government debt burden constraining policymakers’ ability to raise interest rates?

Currency intervention may alter short-term trading behavior but cannot replace monetary policy. As long as Japanese interest rates do not rise further—or US rates do not fall significantly—there remains a rationale for capital to flow overseas.

John Wood, Asia Investment Chief at Lombard Odier, said the intervention’s effect on the yen “may only last for a limited time.” He suggested the Bank of Japan may need at least two more rate hikes to truly establish a defense line against further yen depreciation.

Yen weakness may not be solely due to low interest rates

However, interest rates are not the only reason for the yen’s weakness.

Crédit Agricole CIB points to a deeper issue: an "asymmetry in investment power" between the US and Japan. The US continues to pour vast funds into AI and large-scale investment projects, attracting global capital. In contrast, Japan’s planned public-private investment initiatives have yet to be fully realized.

To correct yen weakness, the key may not simply be raising interest rates, but expanding Japan’s domestic investment opportunities so that the country’s massive pool of domestic savings is willing to stay at home rather than continuously chasing higher returns overseas.

From this perspective, the US-Japan joint intervention resembles setting up a "guardrail" in front of the yen’s depreciation path—preventing disorderly acceleration—but not directly reversing its long-term trend.

160 as a "political red line"—Rapid yen depreciation may force government to act again

Markets believe the 160 level has become a "political bottom line." If the yen again rapidly breaks below this key level in a sharp or disorderly manner, the Japanese government may re-enter the market to intervene.

Moreover, the US and Japan are attempting to strengthen market deterrence against further yen depreciation. Recently, both sides emphasized that the Federal Reserve’s repurchase facility for foreign and international monetary authorities allows Japan to obtain dollar liquidity by using US Treasuries as collateral. This reduces Japan’s need to sell US bonds to fund intervention. US Treasury Secretary Bessent has also repeatedly signaled support for the yen.

This arrangement could indeed increase the cost for markets betting on further yen depreciation. However, it cannot eliminate the fundamental incentives behind yen carry trades. Deterring markets may be easy, but changing capital flows requires altering investment incentives and building trust.

The greatest achievement of this US-Japan joint intervention may be signaling to markets that "160 is not a level that can be breached without cost." But as long as the US-Japan interest rate differential persists and Japanese capital continues chasing overseas returns, the fundamental forces driving yen depreciation remain intact.

More exclusive Wind Media insights: · Just how cheap is the yen? A curry rice meal reveals a harsh truth—market rates vs. public perception in Japan · Customers can’t afford AI chips anymore! NVIDIA teams up with Wall Street on a $500 billion financing plan—what risks are hidden? · Is US debt pressure becoming unbearable? Bessent acts repeatedly—Wall Street starts sensing trouble