Japan Keeps Buying Yen and the Yen Keeps Falling: What 157 Means for Your Portfolio

The yen is stuck around 157 to the dollar, and it has stayed there through a string of interventions that began with the Japanese currency near historic lows.

One of those interventions was genuinely unusual: the United States sold euros for yen, with Japan's own buying coming on top of it. Coordinated intervention between the US Treasury and Japan's Ministry of Finance is rare. It signals that Washington, not just Tokyo, considers the level a problem.

It hasn't worked. The yen jumped after weak US jobs data on 10 August, then settled back. Traders remain leery of further action but unconvinced yen weakness is over. Japanese government bond yields have been rising, and Japanese stocks have fallen on days when the finance minister's language kept traders wary.

Why intervention doesn't fix this

Currency intervention can win a battle. It cannot win a war against an interest rate differential.

The mechanics are simple. If you can borrow in yen at close to nothing and hold dollars earning meaningfully more, you will do it — and doing it means selling yen and buying dollars. That is the carry trade, and it is one of the largest persistent flows in global finance.

Intervention supplies a burst of yen demand. It does not change the arithmetic that made selling yen profitable in the first place. As long as the gap between Japanese and US rates stays wide, the flow reasserts itself, and the intervention has bought time rather than a solution.

The Bank of Japan has been normalising slowly — it left its policy rate unchanged at its late-July meeting, saying it would monitor yen movement, AI, and the Iran war. There's a further wrinkle: a new calculation formula puts Japan's inflation figure below the central bank's 2% target for six months, which reduces the domestic pressure to hike faster.

Why a Canadian or American investor should care

This is not a Japan story. It's a leverage story that ends somewhere else.

In 2024, a sharp unwinding of yen carry trades triggered a 26% Nikkei drawdown in less than a month — and it did not stay in Japan. When cheap yen funds positions in US technology, Mexican bonds, and crypto, an unwind forces simultaneous selling across all of them. Correlations that looked comfortably low go to one, precisely when you need them not to.

That is the mechanism by which a currency you don't own, in a market you don't invest in, shows up as a drawdown in your index fund.

We wrote a guide on what to do when the market falls right after you start investing. This is one of the specific ways that scenario gets triggered — and one of the reasons the answer to it is almost never "sell."

What this does and doesn't change

It doesn't change your plan. You cannot position a long-term portfolio for the timing of a carry trade unwind. Nobody can. Attempts to do so mostly produce transaction costs.

It does explain volatility you'd otherwise misread. If global markets drop sharply on a day with no obvious news, a yen move is a common culprit. Knowing that stops you from inventing a fundamental explanation for a mechanical one.

It argues for genuine diversification, not the appearance of it. Holding seven funds that all fund themselves from the same global liquidity pool is not diversification. What "diversify your portfolio" actually means covers the distinction.

It matters if you hold Japanese equities. A weak yen flatters Japanese exporter earnings and simultaneously erodes your returns when converted back to CAD or USD. Unhedged Japanese equity exposure has been a tug-of-war between those two forces all year.