BOJ Rate Hike Fails to Boost Yen as $2.3 Trillion Carry Trade Unravels

The Bank of Japan (BOJ) raised its benchmark interest rate to 1.25% on September 18th, the highest level since 1995. This decision was met with a surprising market reaction, as the yen's value instead fell.

The USD/JPY exchange rate rose 1.3% intraday to ¥158.05 immediately after the decision and stood at ¥157.41 on September 22nd. Normally, a rate hike would boost a currency's value, but the U.S. Federal Reserve resumed rate increases for the first time in over three years, reinforcing expectations that the U.S.-Japan interest rate differential would not narrow.

Cross-border yen borrowing has ballooned to an estimated ¥360 trillion (approximately $2.3 trillion), up 67% from December 2021 to March of this year. This massive carry trade is a strategy where investors borrow low-interest yen, convert it into higher-yielding currencies like the dollar or Mexican peso, and invest in assets like U.S. stocks and bonds.

The BOJ faces a dilemma: if it doesn't raise rates quickly enough, the U.S.-Japan interest rate differential persists, potentially expanding yen weakness and carry trades further. Conversely, accelerating tightening could trigger the unwinding of massive carry trade positions already accumulated.