The US Treasury and Japan's Ministry of Finance carried out their first coordinated currency market intervention since June 1998, after the yen fell to its weakest level in decades against the US dollar. The slide largely reflects a wide gap between US and Japanese interest rates, which encourages investors to borrow cheaply in yen and invest in higher-yielding assets elsewhere, a strategy known as the carry trade, compounded by Japan's debt load, above 200% of GDP, and rising oil import costs tied to the Iran war.
Japan reportedly spent around ¥8.45 trillion ($52.8 billion) in a single day, likely the largest one-day intervention on record, pulling the yen from around 164 to about 155 per US dollar. The New York Fed directly sold euros to buy yen on behalf of the US Treasury. That choice of euros over dollars surprised markets, with Brookings Institution fellow Robin Brooks arguing it made the operation look less coordinated.
Asked why the US joined in, President Donald Trump told reporters, "Japan's always been very good to us, with the exception, of course, of Pearl Harbour." Beneath the quip is a more practical motive. Japan is the largest foreign holder of US government debt, and had it acted alone, it may have needed to sell part of that holding to fund the buying, pushing up US borrowing costs.
For Australians, the flow-on effect runs through bond markets rather than the yen itself. Higher US Treasury yields tend to weigh on share valuations globally, which matters for retirement savings held in super funds. Analysts also flag risk to South Korea and Taiwan, both central to the chip supply chains behind the AI boom. The recovery may not last, these interventions typically fade without a
