Japan's yen-buying, U.S. dollar-selling intervention cost 2.83 trillion yen ($19 billion) on Sept. 22, then the largest amount spent in a single day, the Finance Ministry said Tuesday.
Since the first intervention in 24 years to prop up the yen, Japanese monetary authorities have likely stepped in multiple times, prompting market sources to estimate a far larger amount has been spent. Before Sept. 22, 2.62 trillion yen spent on April 10, 1998, was the largest daily yen-buying, dollar-selling operation.
Japan's foreign reserves, used to intervene in the market, shrank to $1.19 trillion at the end of October, separate data showed. The reserves, consisting of a variety of assets including foreign securities, deposits and gold, stood at $1.24 trillion a month earlier.
So far, the Sept. 22 operation was the only one immediately announced by Japan during its latest foray into the market, despite the yen surging over a short period of time twice in October.
Finance Minister Shunichi Suzuki has said there are times when the government intervenes without making announcements to maximize the impact.
The yen has been weakening against the dollar this year as financial markets price in the widening interest rate gap between Japan and the United States.
On Sept. 22, Japan intervened after the yen neared 146 versus the dollar as Bank of Japan Governor Haruhiko Kuroda ruled out the possibility of a near-term rate hike. The yen jumped to the 140 zone from around 145.90 in about half an hour.
The impact of the intervention, however, soon petered out, and the yen resumed its decline. A month later, it slipped toward 152, a 32-year low against the dollar, sparking another yen-buying intervention on Oct. 21 that sent the Japanese currency to 146. Another operation likely took place on Oct. 24.
According to the ministry's data for one month to Oct. 27, the government spent a record 6.35 trillion yen to buy the yen for dollars, though no daily breakdowns for the period have been released.
A weak yen cuts both ways. It boosts exporters' profits earned overseas when repatriated, but it inflates import costs for the resource-scarce nation at a time when households are feeling the pinch from rising costs caused by Russia's war in Ukraine.
Suzuki has said it is not specific yen levels but volatility that the government is closely watching, keeping up warnings that necessary steps will be taken to cope with rapid fluctuations.
The BOJ governor, for his part, has said currency moves should reflect economic and financial fundamentals, and that rapid, one-sided yen depreciation is "negative" for the economy, which is being supported by the central bank with monetary easing. The central bank conducts interventions for the Finance Ministry.
Caution about another round of intervention by Japanese monetary authorities has prevented the yen from tumbling past 150 to the dollar. But currency analysts say the diverging policy paths of the BOJ and the U.S. Federal Reserve means the yen's weakness will likely persist. The yen was trading in the 146 zone on Tuesday.