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 rate hike by the Bank of Japan (BoJ) at the September meeting has surged from 22% to 84%. This signals a dramatic shift in market sentiment.
Such a rapid reversal has occurred against the backdrop of a weakening effect from currency interventions by Japanese authorities. The yen, which showed steady gains in late July and early August following coordinated actions by the government and central bank, has come under pressure again. This week, the USD/JPY exchange rate fell by approximately 1%, reaching 159.43, marking the worst weekly performance since May.
In essence, the currency has lost about half of all the gains that followed the intervention. Before the currency measures began, the rate held around 164 yen per dollar. History is repeating itself: after the April intervention, the yen also retreated over several months, approaching multi-year lows.
Notably, Tokyo's former top currency diplomat Mitsuhiro Furusawa recently suggested in an interview that authorities could deploy currency reserves again at any moment. However, he emphasized that officials are also prepared to take more decisive steps—signaling a faster rate hike to support the national currency.
Traders bet on policy tightening
It is precisely this connection between interventions and key rate decisions that explains such a sharp change in expectations on Polymarket. Traders no longer believe in the effectiveness of one-off currency measures and are betting on a fundamental tightening of BoJ policy. According to strategists, particularly from OCBC, interventions alone are insufficient to reverse the yen's dynamics. The currency needs clear support from a central bank willing to tighten monetary policy, especially as inflation approaches the target level.
However, the opposite scenario also carries significant risks. If the BoJ leaves the rate unchanged, the market could react with sharp disappointment, and the yen could once again head toward 160 per dollar. Market participants are now betting on central bank action rather than new interventions.
My view: the sharp jump in probability on Polymarket to 84% looks somewhat excessive. The market tends toward extremes, and such a high estimate could be prone to correction if the BoJ delivers a surprise. However, this signal cannot be ignored—it reflects growing pressure on the Japanese regulator, which finds itself caught between the need to support the currency and risks to the fragile economic recovery.