The US and Japan have just intervened in the currency market together for the first time since 2011. Here’s why it could affect your investments too.
Late last week, two of the world’s largest economies quietly did something they haven’t done together since 2011.
Japan spent an estimated $53 billion to $59 billion buying its own currency.
The United States joined in.
That might sound like an obscure foreign-exchange story. It isn’t.
Currencies influence everything from global capital flows and stock markets to commodity prices and emerging-market currencies like the rand. When governments intervene together on this scale, investors should pay attention because they’re usually trying to prevent a much bigger financial problem.
According to Reuters, Treasury Secretary Scott Bessent’s notebook, photographed during a cabinet meeting at Camp David, included a simple instruction:
“To Do: Buy Japanese Yen (JPY) $5–10 bil.”
On Monday, Japan’s Finance Ministry confirmed that Washington and Tokyo had carried out a coordinated intervention to support the yen — the first joint action since March 2011.
So why has the yen become such a problem?
Why the yen currency became so weak
Over the past five years, Japan has kept interest rates close to zero while the United States steadily raised rates to fight inflation.
That created an unusually profitable opportunity for global investors.
They could borrow money very cheaply in Japan, convert it into US dollars and invest those dollars where interest rates were much higher.
Imagine borrowing at almost 0% in Japan and earning 4% to 5% in the US.
Millions of investors were effectively making the same trade.
Every time they sold yen to buy dollars, it pushed the Japanese currency a little lower. As more investors piled in, the effect snowballed.
By late July 2026, the dollar had climbed to almost ¥164 — the weakest level for the yen since 1986.
A weak currency helped Japan’s exporters by making their products cheaper overseas.
But it also made imports like oil, gas, food and raw materials much more expensive, squeezing Japanese households and businesses.
Why the US got involved
Japan has tried supporting the yen before.
The problem is that markets often ignore unilateral intervention. If the underlying interest-rate gap remains, investors usually resume selling the currency.
American participation changes that.
First, it sends a much stronger signal that both governments want to stop the yen’s slide.
Second, it reduces the amount Japan must spend from its own foreign-exchange reserves. That means Japan is less likely to sell large amounts of US Treasury bonds to finance future interventions — something Washington would prefer to avoid while borrowing heavily itself.
There was another reason.
An exceptionally weak yen makes Japanese exports cheaper in world markets, putting additional pressure on American manufacturers.
For Washington, stabilising the yen wasn’t simply about helping Japan. It also served America’s own economic interests.
What investors should watch
#1: The rand and emerging markets
If coordinated intervention helps weaken the US dollar or improves global investor confidence, emerging-market currencies such as the rand could benefit.
That won’t happen overnight, nor is it guaranteed.
But when the dollar weakens, money often begins flowing back into emerging markets. That can support both local currencies and equity markets, including South Africa.
#2: The carry trade
A stronger yen makes borrowing in Japan less attractive.
Some investors may begin closing those positions by selling overseas assets and repaying yen loans.
If enough investors do this simultaneously, volatility can spread across global markets.
We saw exactly that during the carry-trade unwind in 2024.
#3: Japanese equities:
A stronger currency is generally a headwind for Japan’s export giants. Companies such as Toyota, Sony and Panasonic earn much of their revenue overseas. When those earnings are translated back into a stronger yen, profits become less valuable in local currency terms. The Nikkei’s immediate decline reflected exactly that concern. Investors with Japanese equity exposure through global ETFs or funds should factor this into their return expectations.
Most investors will dismiss this as an obscure currency story.
History suggests that’s exactly when investors get caught off guard.
Major government interventions rarely happen in isolation. They’re usually a sign that policymakers see risks building beneath the surface of global markets.
Whether it’s the rand, global shares or capital flowing into emerging markets, the effects often appear months later—not immediately.
That’s why this isn’t simply a story about Japan.
It’s a story about the forces that could shape investment returns around the world—including here in South Africa.
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