We've spent a lot of time lately discussing how much the U.S. stock market depends on a handful of large tech and AI companies. Today I want to cover a different risk, one developing overseas that could touch nearly every asset class: Japan's yen carry trade.
The idea is simpler than it sounds. For years, investors borrowed money in Japan at almost no interest, converted it to dollars, and bought higher-returning assets like U.S. stocks, bonds, real estate, and crypto. As long as Japanese rates stayed low and the yen stayed weak, it worked beautifully.
The danger appears when the yen suddenly strengthens or Japanese rates rise. Then investors have to sell those assets and buy yen to repay their loans. If that happens too fast, it creates forced selling across global markets. That's called a carry-trade unwind.
What just happened in Japan.
The Bank of Japan raised its policy rate to about 1% in June, its highest in decades, and held it there in July, though one member pushed for more. Meanwhile the yen had fallen to nearly ¥164 against the dollar, its weakest in roughly 40 years, prompting a rare coordinated U.S.-Japan intervention that pushed the dollar back to around ¥155.
That's a big currency move in a short window. For anyone who borrowed in yen and invested in dollars, a rapidly strengthening yen can wipe out returns, and if leverage was involved, force selling through margin calls.
Why oil and Iran matter.
Japan imports most of its energy, so it's especially vulnerable when oil rises while the yen falls. It gets hit twice: oil costs more, and each dollar to buy it costs more yen.
The Iran conflict disrupted shipping through the Strait of Hormuz and pushed oil above $100 at its peak. Prices have since pulled back, but U.S. crude remains roughly 20% above pre-conflict levels. If the conflict escalates again, higher oil would raise Japanese inflation and pressure the BOJ to hike rates.
That's where the risks feed each other: higher oil raises Japanese inflation, the BOJ raises rates, the yen strengthens, leveraged carry trades unwind, investors sell global assets, and volatility spreads. If Japan sells U.S. Treasuries in the process, our yields and mortgage rates could feel upward pressure too.
How likely is a carry-trade unwind?
Nobody knows the exact size of the carry trade, so any estimate is a judgment call, not a certainty. Based on current conditions, here's how I see the rest of 2026.
Base case (55–65%): A gradual unwind. The BOJ moves cautiously and investors slowly reduce leverage. Expect more frequent 5% to 10% pullbacks, especially in tech, AI, small-cap growth, and crypto, but not necessarily a crash.
Stress case (25–35%): A disorderly unwind. If the BOJ hikes again, the yen strengthens fast, and oil tops $100, we could see a quick 10% to 20% correction, with the most crowded and leveraged assets hit hardest.
Crisis case (10–15%): A global financial accident. This requires several problems at once. It's not my base case, but the odds are high enough not to ignore.
What it could mean for your stocks and 401(k).
A carry-trade unwind wouldn't hit everything equally. The biggest risk is in high-valuation, heavily leveraged, crowded positions, which includes the large tech and AI names that now dominate the S&P 500 and Nasdaq.
Here's the part many people miss: even if you don't own tech stocks directly, you probably own them through your 401(k). An S&P 500 fund, a growth fund, a tech fund, and a target-date fund can all hold the same handful of companies. That's concentration disguised as diversification, and in a selloff they can all fall together.
This isn't about timing the market. It's about making sure one global event can't derail your whole retirement plan. Worth reviewing: how much of your account sits in large-cap tech, whether your funds overlap, and whether your mix still fits your timeline, especially if you're near retirement and exposed to sequence-of-returns risk.
What it could mean for real estate.
It depends on how the unwind affects Treasury yields and inflation.
If investors flee to safety and pile into Treasuries, yields, and eventually mortgage rates, could fall, which would help affordability and housing demand. But if Japan sells Treasuries while oil keeps inflation high, yields and mortgage rates could stay elevated or rise, pressuring affordability, property values, and financing. And if the unwind triggers a broader slowdown, transaction volume usually falls first as sellers cling to old prices and buyers wait.
For real estate investors, the priorities are debt structure and cash flow. Long-term fixed-rate debt with healthy reserves is far better positioned than anything dependent on refinancing or short-term floating-rate loans. Disruption can also create opportunity, but only if a property produces sustainable cash flow under realistic financing assumptions. A lower price alone isn't a deal.
I'm not predicting the financial system is about to collapse. My base case is a gradual unwind with more volatility, not a crash.
But Japan, oil, the Iran conflict, the Treasury market, and the concentration of the U.S. stock market are no longer separate stories. They're increasingly connected. If the BOJ has to raise rates while defending the yen, it could accelerate money moving out of U.S. assets and back toward Japan.
The answer isn't panic. It's preparation: understand your exposure, reduce unnecessary leverage, keep liquidity available, review your 401(k), and make sure your real estate can survive higher rates and a temporary dip in demand.
Periods of stress create real opportunities, but they usually go to the investors who prepared before the volatility arrived.
This article is intended for educational purposes only and should not be considered individualized investment, tax, or legal advice. Probability estimates represent the author's scenario analysis and are not guarantees of future results.
