Unwinding the Yen Carry Trade: How Japan's Shifting Rate Policy Impacts Global Markets

Sep 16

4 min read

For nearly two decades, one trade has quietly underpinned liquidity across global markets: borrow cheaply in Japanese yen, then invest the proceeds in higher-yielding assets elsewhere. It's called the yen carry trade, and it works only for as long as Japanese interest rates stay far below the rest of the world's. That gap is now closing faster than markets expected, and September 2026 could be the month it narrows the most sharply yet.

What Is the Yen Carry Trade?

The mechanics are straightforward. An investor borrows yen at Japan's near-zero interest rates, converts that yen into another currency, and invests it in higher-yielding assets abroad - U.S. Treasuries, emerging-market bonds, equities, or leveraged derivatives positions. The profit is the spread between what the investor pays to borrow yen and what the foreign asset returns, plus any gain if the yen weakens further against the funding currency in the meantime.

The trade has grown large enough that it now functions as a source of global liquidity in its own right. When conditions are calm, unwinding it slowly is manageable. When the yen suddenly strengthens or Japanese rates rise unexpectedly, the trade can unwind fast - forcing leveraged investors to sell assets across markets to repay yen loans, which is the volatility dynamic seen in August 2024 and again feared today.

The July Intervention

The yen had been sliding for years on the back of near-zero Japanese rates, and by late July 2026 it touched roughly 163 per dollar - near its weakest level in more than three decades. On July 30 and 31, Japan's Ministry of Finance sold an estimated $85 billion to buy yen, and the U.S. joined in by selling euros to buy yen without disclosing the amount - an unusually coordinated and publicly acknowledged intervention for both countries.

It worked, briefly: the yen strengthened about 5% to touch 155 per dollar. But by mid-August it had given back much of that move, weakening to around 159. According to Morgan Stanley Research, the intervention's purpose may have been less about defending a specific exchange rate and more about squeezing speculative carry positions and buying time for the Bank of Japan to normalize policy without triggering a disorderly market move.

The September Rate Decision

The Bank of Japan meets on September 17–18, and market pricing has shifted decisively toward a hike. A Bloomberg survey of 52 BOJ watchers found all of them expect a 25-basis-point increase to 1.25% at this meeting, with roughly 93% expecting a follow-up hike by January 2027. U.S. Treasury Secretary Scott Bessent has added public pressure, saying he expects Japan's government and the BOJ to act in ways that strengthen the yen. Reuters has separately reported that the BOJ is weighing a faster overall pace of tightening than its historical rhythm of roughly two hikes a year, citing inflation pressure from Middle East tensions, AI-driven demand, and persistent yen weakness.

Why does a quarter-point move matter so much? Because the carry trade's profitability is a spread, not an absolute number. Every basis point the BOJ adds narrows that spread against currencies like the dollar, increasing the incentive for leveraged holders to unwind early rather than be caught by a larger, later move.

Why It Reaches Beyond Japan

Japanese investors are among the largest foreign holders of U.S. Treasuries. Morgan Stanley's research notes that higher Japanese rates could prompt some of that capital to repatriate, pushing Treasury yields higher and raising borrowing costs across the U.S. economy - from mortgages to corporate debt, even in portfolios that hold no yen exposure at all. This is why the Fed and BOJ are, in effect, watching each other: Morgan Stanley's Seth Carpenter argues the yen's longer-term trajectory depends more on U.S. monetary policy than on the BOJ or on intervention, since the BOJ is still viewed as “behind the curve” until it moves rates meaningfully higher.

The Case for a Smoother Path

Not every market observer expects disorder. The argument for a more manageable outcome generally rests on a few points worth weighing:

A 25bp move to 1.25% is well-telegraphed and largely priced in by markets, unlike the surprise hikes that triggered the August 2024 carry unwind - markets rarely panic over an outcome they've already priced.
The BOJ has signaled a gradual, quarterly pace rather than an aggressive tightening cycle, giving leveraged investors time to reduce exposure in an orderly way rather than all at once.
The July intervention already flushed out some speculative positioning, meaning the trade may be less crowded than it was in 2024, reducing the scale of any forced unwind.

What to Watch Next

September 17–18: BOJ policy decision - a hike to 1.25% is close to fully priced in; the reaction will hinge on tone and forward guidance more than the move itself.
U.S. inflation and jobs data, and Fed commentary - Morgan Stanley frames the yen's fair-value path (estimated at 165–167 currently, drifting toward 155 over time) as tied more to the Fed's rate path than to Japan's.
Movements in U.S. Treasury yields, since Japanese investor flows are a transmission channel into U.S. borrowing costs.

Conclusion

The yen carry trade has functioned for years on a simple premise: cheap Japanese borrowing costs relative to the rest of the world. As the Bank of Japan closes that gap, the trade's profitability erodes at the margin, raising the odds of a gradual unwind. Whether that unwind stays orderly or spills into broader volatility will likely depend less on the size of September's expected hike and more on how clearly the BOJ communicates its path forward and on how the Federal Reserve responds in turn.