Over the past year, a surge in debt issuance by artificial intelligence companies has placed upward pressure on borrowing costs, partly due to increased bond supply pushing yields higher. These developments have contributed to investor concerns about the impact of rising interest rates on corporate profits and, by extension, the stock market.

A recent move in Japanese government bond yields has played a significant role in this dynamic. Japan, which holds more than $1 trillion in U.S. Treasury securities and is the largest foreign holder of U.S. government debt, faced a depreciating yen that fell to a 40-year low. Typically, such sharp currency declines prompt the Japanese government to sell U.S. Treasuries to bolster the yen. This potential selling pressure raised fears of higher U.S. Treasury yields, which would increase borrowing costs for companies and potentially disrupt stock markets already sensitive to rising expenses.

Further compounding these jitters were comments from Kevin Warsh, the newly appointed chair of the U.S. Federal Reserve, which contributed to a rise in the 10-year Treasury yield—a benchmark rate that influences borrowing costs for both corporations and consumers. The yield reached its highest level during the second presidency of Donald Trump before the U.S. Treasury intervened in currency markets.

The Treasury’s action to support the yen helped stabilize the debt market and eased apprehension over climbing borrowing costs among AI companies. Market reactions were swift: Treasury yields declined and stock prices rose, aided also by strong earnings reports from major firms such as Amazon and Palantir.

Analysts note, however, that the intervention carried risks. Strengthening the yen excessively could lead investors to shift capital away from U.S. assets and toward Japanese markets, where rising bond yields might offer more attractive returns. George Goncalves, a macro strategist at MUFG Securities, remarked that policymakers must strike a careful balance, aiming to support the yen “just enough” to avoid triggering an unwinding of large carry trades—investment strategies that capitalize on low borrowing costs in yen versus higher returns abroad.

Japan’s prolonged period of low growth and inflation kept its interest rates near historic lows, contrasting sharply with other economies like the U.S., where central banks have raised rates to combat inflation following the pandemic. This divergence has fueled yen carry trades, which the Bank of International Settlements estimates to involve hundreds of billions to several trillion dollars.

Sustained strengthening of the yen would raise the costs of these carry trades, potentially forcing traders to unwind positions financed by yen borrowing and exerting downward pressure on U.S. equity markets. Policymakers in the United States appear keen to manage this complex situation delicately, balancing the global interconnectedness of interest rates, currency values, and market stability.

“This is the quintessential global macro dilemma that we knew would happen and it’s starting to bubble up to the surface,” Goncalves observed, underscoring the intricate interplay among these factors as markets navigate the evolving economic landscape.