U.S. Treasury Warns Against Excessive Yen Volatility, Calls on BOJ to Continue Raising Interest Rates
N.R. Finch
The U.S. Treasury called excessive yen volatility 'undesirable' in its semi-annual currency report, publicly urging the Bank of Japan to keep raising rates — a rare external endorsement of another central bank's tightening path, where the signal matters more than the policy itself.
What exactly did the U.S. Treasury say?
The semi-annual currency report's core judgment: yen volatility is "undesirable," and monetary-policy normalization — i.e. rate hikes — would help anchor inflation expectations and reduce excessive FX swings.
On the day the report dropped, the yen hit its weakest level against the dollar in roughly four decades. This means → Washington chose to speak up at the yen's lowest point; the timing itself is the signal.
The Treasury added that it will continue close consultations with Japan's Ministry of Finance on macro and FX issues.
How far has the yen actually fallen?
From late 2011 through April 2026, the yen's real effective exchange rate and its dollar rate both fell a cumulative 51%. The report calls this "substantial yen undervaluation."
In plain terms = over fifteen years the yen's purchasing power halved — the same amount of money buys roughly half as much.
Nominal wages in Japan have risen, but inflation has pressured household real purchasing power — pay went up, prices went up faster.
The BOJ is already hiking — why isn't it enough?
Since exiting ultra-loose policy in 2024, the BOJ has raised rates multiple times. In June it lifted the policy rate to 1%, a 31-year high.
Yet even as the U.S.–Japan rate gap narrows, yen depreciation pressure persists. This reflects a market view that the current pace of hikes is still too slow to reverse the trend.
The BOJ has signaled willingness to keep tightening, but its pace is constrained by domestic political pressure.
Where is the biggest resistance to further hikes?
The market's core concern: dovish Prime Minister Sanae Takaichi may push back against further rate increases.
This means → even if the BOJ wants to hike, it faces a political tug-of-war with the Prime Minister's office — monetary policy is not the central bank's call alone.
Japanese authorities have warned they may intervene in markets if FX swings become excessive, but traders remain skeptical about intervention's real effectiveness.
What does America's statement really mean?
A U.S. Treasury publicly backing another country's central bank to raise rates is extremely rare — the convention is to respect central-bank independence and stay quiet.
In plain terms = Washington is saying: "We think you should hike, and we don't mind saying so on the record."
This gives the BOJ's tightening path an external endorsement, but whether domestic political resistance can be overcome remains the key variable markets are watching.
Content is for reference only, not financial advice.