The $87 billion spent on the yen is not a number Japan published

The $87 billion said to have been spent defending the yen is not a figure the Japanese government published. It is an estimate, reconstructed by a private analyst from movements in the Bank of Japan's current account balances.

Japan and US confirm rare joint intervention to prop up yen (Al Jazeera, 2026-08-03)

출처: aljazeera.com

That the intervention happened is confirmed. Japan and the US bought yen together across July 30 and 31, and on August 3 the finance authorities of both countries acknowledged it. It was the first time the two had bought yen side by side since 1998.

The finance ministry has released no number at all

Japan's Ministry of Finance discloses intervention amounts once a month as a range, and the exact day-by-day figures come later, in a quarterly release. The most recent disclosure covers June 29 to July 29 and came out on July 31. This intervention began the day after that window closed. The next release falls around September 1. So that amount is, for now, a figure that cannot be checked. Other estimates of the same two days differ. One puts Thursday alone near $59 billion; another splits it as roughly $75 billion from Japan and $5 to $10 billion from the US. The estimates sit close to $10 billion apart from one another.

Half of the gain has gone back

Just before the intervention the yen was at 163 to 164 per dollar, its weakest in forty years. In the days after, it strengthened to 155.20. On August 11 it stood at 159.25. It gained 8.8 yen and handed back 4.05, so 46% of the move is gone.

Did the 1998 intervention work

In the joint operation of June 17, 1998, the US side spent $833 million. The yen moved from 146.67 to 136.51 per dollar. Two months later, in August, it was back at 147 to 148. The trend broke in October of that year. The Russian crisis and the collapse of a large hedge fund unwound, all at once, the trade of borrowing yen to buy other assets. The intervention did not turn the direction; the direction turned only after the terms of borrowing changed.

The same pattern repeated in 2022 and 2024. Japan spent 6.35 trillion yen alone in October 2022 and the yen still went through 150 afterwards, and the 9.79 trillion yen of April and May 2024 was retraced within two months. What turned 2024 was the Bank of Japan raising rates at the end of July.

What the September 18 Bank of Japan meeting will settle

So it is more useful to ask what makes an intervention hold than whether this one worked. The US policy rate sits in the high 3% range; Japan's is 1%. On ten-year government bonds it is 4.7% against 2.8%.

While that gap stands, borrowing yen to hold another currency pays, and buying yen in the market does not remove the incentive. How much was spent over those two days is settled around September 1. Whether the money meant anything is settled on September 18. If the Bank of Japan lifts its policy rate above 1%, the job of holding the yen up passes from intervention to interest rates; if it holds, the yen's direction goes back to depending on US rates and on the ministry's next purchase.