Both central banks tightened this week. The spot policy-rate gap did not narrow, and investors are pricing the next moves more differently than the current settings suggest.
The Federal Reserve lifted the federal-funds target range by 25 basis points on September 16 to 3.75% to 4.00%. On Friday, September 18, the Bank of Japan raised its overnight call-rate guideline from 1.0% to about 1.25%. The Fed vote was unanimous; the BOJ vote was 7-2.
Both 25bp moves left the spot gap exactly where it was. Using the midpoint of the Fed range, the U.S.-Japan policy-rate differential is 2.625 percentage points, the same as before this week's decisions.
The yen still weakened after the BOJ decision, falling as much as 1.3% in Friday trading. U.S. two-year Treasury yields reached 4.744% intraday, the highest since July 2024, while the 10-year yield approached 5%.
The market is repricing the next meeting, not this one
The Fed's statement described activity as expanding at a solid pace, household spending as resilient and inflation as elevated. That combination leaves the central bank with room to tighten again if inflation remains broad. By Friday, futures cited by The Wall Street Journal assigned a 58% probability to another Fed increase in October.
The BOJ also left the door open to further tightening, but Governor Kazuo Ueda did not give investors a timetable. Two dissenters and the absence of stronger forward guidance helped keep expectations for rapid follow-through contained.
Expected persistence explains more of the currency move than the matched 25bp decisions. A dollar-yen position still earns a large policy-rate advantage today, while Friday's market action implied that investors expect the gap to close slowly.
The yen needs expected-path convergence
Friday repriced the forward path more than the current policy gap. A further BOJ hike would matter most if it changes expectations for the cumulative Japanese tightening cycle, or if U.S. inflation data reduce the expected peak in Fed rates. A single matched 25bp move on each side leaves the current carry arithmetic unchanged.
Rates books should separate spot carry from expected convergence. This week's decisions left the current U.S.-Japan policy gap unchanged while markets repriced the path several meetings ahead.
Sources
- Federal Reserve, September 16 policy statement: https://www.federalreserve.gov/newsevents/pressreleases/monetary20260916a.htm
- Federal Reserve, H.15 rates: https://www.federalreserve.gov/releases/h15/
- Bank of Japan, 2026 monetary-policy decisions: https://www.boj.or.jp/en/mopo/mpmdeci/state_2026/index.htm
- Financial Times, September 18 yen reaction: https://www.ft.com/content/97a0bed5-0580-4ccc-bd3c-fe9a714259e2
- Wall Street Journal, September 18 U.S. Treasury repricing: https://www.wsj.com/finance/investing/two-year-u-s-treasury-yield-reaches-new-multi-year-high-99d3112b