The market is pricing in an 84% probability of a rate hike by the Bank of Japan in September.
Participants on the decentralized prediction platform Polymarket have sharply revised their expectations regarding Japan's monetary policy. In just two weeks, the probability of a key interest rate hike by the Bank of Japan at its September meeting has surged from 22% to 84%. This signals a dramatic shift in market sentiment, which is now confident that the regulator will tighten its policy course.
Why the yen is weakening again
The trigger for this reversal was the fading effect of currency interventions by Japanese authorities. This week, the yen lost about 1% against the dollar, falling to 159.43 — its worst weekly performance since May. The currency has retreated by roughly half of the gains it posted after coordinated interventions in late July and early August, when the exchange rate was held near 164 yen per dollar.
Historical dynamics show that one-off interventions rarely change the long-term trend. After April's injections, the yen slid back to 40-year lows within a few months. It appears we are witnessing a repeat of this scenario.
Betting on the central bank's resolve
The key signal to the market is the Bank of Japan's readiness to move from verbal interventions to concrete action. Tokyo's former top currency diplomat Mitsuhiro Furusawa emphasized that authorities could deploy reserves at any moment, as well as signal a faster rate hike to support the national currency.
OCBC strategists agree that interventions alone are insufficient to reverse the yen's dynamics. Unsurprisingly, the yen has given up ground again. Sustained support for the currency requires a clear stance from the central bank, willing to tighten monetary policy. Inflation in Japan is approaching the target level, providing a fundamental basis for such a move.
The probability of the opposite scenario — keeping the rate unchanged — carries significant risks. The market would immediately react with disappointment, and the yen could once again plunge toward the 160-per-dollar level. Market participants are now betting on central bank action, not on new currency interventions.
My view: the sharp jump in probability on Polymarket reflects not so much confidence in the data as the market's desperate hope that the Bank of Japan will finally move from defense to offense. However, given the history of "disappointments" from the BOJ, I would not rule out high volatility in the yen in both directions right up until the meeting itself.