A four-decade low for the yen has put currency traders on alert for the return of one of finance's bluntest tools: a government raid on the foreign-exchange market.

A four-decade low

The yen touched roughly 161.96 per dollar in trading early this week, Bloomberg reported — the weakest reading since December 1986, narrowly past the level that had already triggered a record intervention in 2024. (The rate is a live market figure that moves continuously.) A weaker yen means more yen are needed to buy a dollar; at 162, the currency is far below the roughly 110 per dollar of just five years ago.

Why it keeps falling

The root cause is a wide gap between Japanese and U.S. interest rates. The Bank of Japan recently raised its benchmark to about 1 percent — its highest since the 1990s — but that remains far below U.S. rates, with Japanese government-bond yields near 2.6 percent against roughly 4.5 percent on U.S. Treasuries. That gap fuels the "carry trade": investors borrow cheaply in yen, convert to dollars and buy higher-yielding American assets, selling yen in bulk along the way. "Investors favor dollar-denominated assets on expectations the Federal Reserve will keep interest rates higher for longer than the Bank of Japan," ING analysts noted, per Yahoo Finance. Japan's aging population, heavy debt and energy imports limit how fast Tokyo can raise rates to close the gap.

What 'intervention' means

When Japanese officials intervene, the Ministry of Finance directs the Bank of Japan to buy yen using the country's foreign reserves — mostly dollars and Treasuries — to prop up the exchange rate. It is expensive and only sometimes effective. Tokyo spent a record ¥11.73 trillion (about $72.5 billion) over a month this spring to push the yen back toward 155, Nippon.com reported, only to watch it slide all the way back. Finance Minister Satsuki Katayama has said authorities stand ready for "bold action" against excessive moves and has discussed currency policy with U.S. Treasury Secretary Scott Bessent — a notable signal, since Washington's acquiescence matters before Tokyo acts at scale. Traders are watching whether the yen breaks decisively past 162, especially around the thin-liquidity July 4 U.S. holiday.

A two-sided problem

A weak yen is not all bad for Japan. Exporters like Toyota and Sony earn abroad and convert profits home at favorable rates, helping lift Japanese stocks to records, and inbound tourism is booming as Japan becomes strikingly cheap for visitors. But households feel the downside: Japan imports nearly all its oil, gas and much of its food, and a cheaper yen pushes up those prices — feeding inflation in a form consumers don't welcome, and adding political pressure on the government. For now, the standoff between market forces and Tokyo's pocketbook remains unresolved.