The most dangerous trades in markets aren't the ones everyone is watching.
They're the ones hiding inside the plumbing.
Japan's carry trade has quietly funded trillions in US assets for decades. Borrow yen at near-zero rates. Convert to dollars. Park in Treasuries, tech, anything with yield. Collect the spread. Repeat.
That spread is now at 1.91%. The lowest it has been since the COVID crash.
We built a carry trade stress model from scratch, 5,333 trading days, 2003 to 2026, to test what this compression actually means for US equities. Here is what we found.
Four inputs. One signal.
US 10Y minus JGB 10Y rate differential. USD/JPY 20-day direction. JGB 40Y yield level. Three thresholds. Four signal tiers: GREEN, YELLOW, ORANGE, RED.
We then ran Newey-West autocorrelation-corrected t-tests on every tier. Standard significance tests overstate confidence when stress periods cluster in time. We corrected for that.
WHAT THE DATA SAYS
GREEN (69.5% of days): +0.70% average 20d SPY return. 65% win rate. p=0.0008 after correction.
YELLOW (17.1% of days): looked significant at p=0.0014. After Newey-West correction, p=0.33. Not significant. YELLOW is statistically indistinguishable from GREEN.
ORANGE (13.3% of days): +1.48% average 20d return. 70% win rate. p=0.0105 after correction. The only stress tier that survives rigorous testing.
The uncomfortable truth: carry stress has historically been bullish for equities, not bearish. Most ORANGE periods coincided with Fed cutting cycles, where lower US rates compressed the differential but also lifted asset prices.
THE PART EVERYONE MISSES
Carry stress alone does not cause crashes. But look at the 7 major SPY drawdowns since 2007.
The 4 drawdowns where yen strengthening was present averaged -29.9%. The 3 drawdowns without carry involvement averaged -20.0%. The GFC: -56.5% in 517 days, had yen strengthening on 61% of trading days during the episode.
Carry stress doesn't ignite the fire. It pours gasoline on it.
And there is one more signal worth watching. During ORANGE periods, TLT averages -0.82% over 20 days at only 37% win rate. Highly significant. Bonds sell off alongside equities. The traditional flight-to-quality hedge disappears exactly when you need it most.
WHY THIS TIME IS DIFFERENT
Every prior ORANGE period in our data was driven by the Fed cutting rates; yen weakness was the byproduct of US monetary easing. The equity market rose because cheap money was flowing.
This ORANGE period is driven by the BOJ hiking. The compression is coming from Japan, not from Washington. The JGB 40Y is at 3.633%, a level reached on fewer than 225 trading days in our entire dataset. The mechanism is structurally different.
The closest historical analog in our data is February 2020. ORANGE signal. Rate differential averaging 1.11%. Yen strengthening on 73% of days during the episode. That drawdown was -34.1% in 33 days.
THE SIGNAL RIGHT NOW
Signal: ORANGE
Rate differential: 1.911%, inside the danger zone
JGB 40Y: 3.633%, above the 3.0% RED threshold
Pseudo-RED Loose: ACTIVE
Cushion to RED: 0.411%
One BOJ hike or one Fed cut closes that gap.
THE TRADE
Carry stress alone is not a reason to go short US equities. The data does not support that.
But the cross-asset picture is the actionable piece.
If you are long equities in an ORANGE regime, your bond hedge is broken. TLT has historically sold off during ORANGE. The 60/40 portfolio does not protect you the way it usually does.
The position: stay long equities, short duration. Reduce TLT, IEF, and long-dated bond exposure. If you want a carry stress hedge, FXY, the yen ETF averages -0.68% during ORANGE periods, meaning yen strength is NOT the dominant dynamic yet. A small long FXY position is cheap optionality on a genuine unwind.
The trigger to watch: USD/JPY breaking below 150. That is when yen strengthening becomes disorderly. That is when ORANGE becomes RED. That is when the gasoline ignites.
150 is the line. We are at 158.
Keep watching.
$SPY $SPX $QQQ $JPY #Japan #BOJ