The U.S. Treasury’s decision to buy Japanese yen this summer was unusual.
Treasury Secretary Scott Bessent has now explained why Washington was willing to intervene directly in a foreign-exchange market: officials feared a disorderly yen collapse could become a global financial-stability problem.
The yen is weakening again after briefly recovering from a 40-year low near 164 per dollar, moving back toward the closely watched 160 level.
What Is the Yen Carry Trade?
Japan has historically had very low interest rates. That encouraged investors to borrow in yen and invest the money in higher-yielding assets elsewhere.
This is broadly known as the yen carry trade.
The trade works well when the yen remains weak and funding costs stay low. It can become unstable when the yen suddenly strengthens or Japanese rates rise. Investors may then need to unwind leveraged positions quickly.
How Could Yen Moves Affect U.S. Stocks?
If carry trades unwind sharply, investors may sell U.S. assets to repay yen funding. That can increase volatility in equities and bonds.
The relationship is not mechanical, but large, sudden currency moves can become a catalyst when financial positioning is crowded.
Why Could U.S. Borrowing Costs Rise?
Japan is one of the world’s largest pools of savings and Japanese investors hold significant amounts of foreign bonds, including U.S. Treasuries.
If currency volatility or higher domestic yields make Japanese assets more attractive, capital can shift away from U.S. fixed income. Lower foreign demand for Treasuries can put upward pressure on U.S. yields.
Higher Treasury yields then feed into mortgages, corporate debt and equity valuations.
What Should Investors Watch?
Three signals matter most:
- USD/JPY around the 160 level, - Japanese government bond yields and Bank of Japan policy expectations, - and U.S. Treasury yields.
The yen is no longer just a currency-market story. It is now a macro variable equity investors should watch more closely.