The Bank of Japan Is 'Behind the Curve' on Rate Hikes, and the Biggest Carry Trade Unwind in a Generation Could Follow

On February 18, Bank of Japan board member Kazuyuki Masu delivered a speech that most American investors never read but probably should have. Further interest rate hikes, he said, will be necessary to complete Japan's monetary policy normalization. Two days earlier, Japan's former top currency official went further, telling Bloomberg that the Bank of Japan is "behind the curve" on taking policy action and that "steady and gradual interest rate hikes can respond to inflation, curb excessive yen depreciation and stabilize long-term bond yields."

These are not fringe opinions from academic observers. These are signals from inside and around Japan's central bank that the next rate hike is coming, that it will not be the last, and that the consequences for global financial markets will be profound. The reason is a three-letter word that most retail investors have never encountered but that institutional traders obsess over: the carry trade.

What the Carry Trade Is and Why It Matters

The yen carry trade is one of the largest and most consequential strategies in global finance. The mechanics are simple: investors borrow money in Japanese yen at very low interest rates, convert it to a higher-yielding currency like the U.S. dollar or Australian dollar, and invest it in assets that earn a higher return than the borrowing cost. The difference between what they earn and what they pay in interest is pure profit, as long as the yen does not strengthen significantly against the target currency.

For decades, Japan's ultra-low and even negative interest rates made the yen the funding currency of choice for this strategy. The trade was so popular and so large that estimates of its total size range from $2 trillion to $4 trillion, though the exact figure is impossible to pin down because much of it occurs through derivatives and off-balance-sheet instruments.

The carry trade works beautifully in a stable interest rate environment. But when the Bank of Japan raises rates, two things happen simultaneously: the cost of borrowing in yen increases, compressing the profit margin, and the yen tends to strengthen as higher rates attract capital back to Japan. Both forces push carry trade investors to unwind their positions, selling the assets they purchased with borrowed yen and buying yen back to repay their loans.

When this unwinding happens at scale, it can create violent dislocations across global markets. We saw exactly this in late July and early August 2024, when speculation about a BOJ rate hike triggered a partial carry trade unwind that sent the Nikkei 225 down 12.4% in a single day, its worst crash since 1987, and rattled equity markets worldwide.

Why This Time Could Be Bigger

The July 2024 scare was triggered by a 25 basis point hike from 0.0% to 0.25%. The Bank of Japan has since raised rates to 0.75%, the highest level in 30 years. And the signals from Masu and others suggest the next hike could come as soon as June 2026, with the International Monetary Fund projecting two more hikes this year and another in 2027.

Each successive rate increase narrows the interest rate differential between Japan and the rest of the world, making the carry trade less profitable and increasing the incentive for investors to unwind their positions. The math is straightforward: when Japan's rate was near zero and U.S. rates were above 5%, the spread was enormous and the carry trade was highly profitable. As Japan's rate climbs toward 1.0% or higher and U.S. rates potentially decline, the spread compresses and the risk-reward calculus shifts.

The potential magnitude of the unwinding is what should concern American investors. If even a fraction of the estimated $2 to $4 trillion in carry trade positions are unwound rapidly, the selling pressure on the assets those positions are invested in, which include U.S. Treasuries, U.S. equities, emerging market bonds, and Australian real estate, could be substantial.

Japan's Inflation Problem

The reason the Bank of Japan is being pushed toward further rate hikes is that Japan's inflation problem has become impossible to ignore. Consumer prices have been above the BOJ's 2% target for nearly four years, the longest sustained period of above-target inflation in modern Japanese history. Food prices have been rising at a pace that is causing genuine hardship for Japanese households. And the weak yen, which has depreciated significantly against the dollar over the past three years, has been a primary driver of imported inflation.

The BOJ faces a dilemma that is the mirror image of the Federal Reserve's. The Fed is worried about cutting rates too quickly and reigniting inflation. The BOJ is worried about raising rates too quickly and derailing Japan's fragile economic recovery. But the pressure from rising prices is making the case for inaction increasingly difficult to defend.

Board member Masu explicitly noted that raising rates would help reduce the policy divergence between Japan and other major economies, a divergence that has been "widely seen as a key driver of prolonged yen weakness that has pushed up import costs for businesses and households." In other words, the BOJ recognizes that keeping rates too low is itself creating economic harm through a weak currency, and that further normalization is necessary to address it.

What American Investors Should Watch

The direct exposure of most American portfolios to Japanese interest rates is minimal. Few retail investors hold significant positions in Japanese equities or bonds. But the indirect exposure, through the carry trade's influence on global asset prices, is substantial and often invisible.

When carry trade positions are unwound, the selling pressure tends to be concentrated in the assets that carry trade investors favored. Historically, these include U.S. Treasury bonds, particularly longer-duration maturities, U.S. technology stocks, emerging market sovereign debt, and commodity-linked equities. An unwinding event could cause Treasury yields to spike temporarily as Japanese and other carry trade investors sell their holdings, creating a paradoxical situation where yields rise even as the economic outlook deteriorates.

The currency implications are equally important. A strengthening yen typically coincides with a weakening dollar, which would benefit American investors with international portfolio exposure but hurt the earnings of U.S. companies that derive significant revenue from Japan and Asia.

The most useful leading indicator for American investors is the USD/JPY exchange rate. If the yen begins strengthening rapidly, particularly below the 140 level, it could signal that carry trade unwinding is accelerating. The VIX, the market's fear gauge, would also likely spike during any disorderly unwinding, as it did during the August 2024 episode.

Preparing for the Unwind

The carry trade unwind is not a certainty. The Bank of Japan could move more slowly than expected. The yen could remain weak if other factors dominate. And institutional investors who learned from the August 2024 scare may have reduced their carry trade exposure or hedged their positions more carefully.

But the direction of travel is clear. Japan is normalizing monetary policy after three decades of ultra-accommodation. Each rate hike brings the world closer to a tipping point where the carry trade becomes unprofitable at scale. And when that tipping point arrives, the repricing could be swift, disorderly, and global.

American investors do not need to panic. They do need to understand that an obscure-sounding strategy involving Japanese interest rates is one of the most important risk factors in global markets today, and that the signals from Tokyo this week suggest the clock is ticking.