The Federal Reserve has started raising interest rates again, but the move is creating an uncomfortable problem for American investors. Higher yields are making bonds more profitable to hold, yet Treasurys are no longer providing the same protection investors once expected when stocks turn volatile.
The Fed raised its benchmark rate by a quarter percentage point on Sept. 16 to a range of 3.75% to 4.00%, its first increase in three years, and policymakers left the door open to another increase this year. Normally, higher rates would make bonds more attractive relative to stocks. This time, the comparison is less straightforward.
Stocks and bonds have increasingly moved in the same direction since 2022. When equity markets come under pressure, bond prices have also become more likely to fall, weakening one of the basic reasons investors hold both assets. That matters to Americans whose retirement accounts, pensions and diversified portfolios have long relied on bonds to cushion losses when stocks decline.
The shift is particularly important in the U.S. Treasury market. Investors are demanding a larger term premium, meaning they want more compensation for the risk of holding longer dated government debt. Heavy federal borrowing, uncertainty over future interest rates and weaker demand from some traditional overseas buyers are adding to that pressure.
Artificial intelligence is making the equation even more complicated.
The same AI investment boom supporting earnings expectations for major U.S. technology companies is also creating enormous demand for capital. Big technology companies are increasingly turning to bond markets to finance data centers, computing infrastructure and other AI spending, adding another wave of debt supply to a market already absorbing large amounts of U.S. government borrowing.
That creates pressure on both sides of the traditional stock and bond trade. AI spending can support corporate profits and equity valuations, while the financing required to build that infrastructure adds to competition for investor capital in the bond market.
The result is a market in which higher interest rates do not automatically make bonds the safer or more attractive choice.
NH Investment and Securities, one of South Korea’s major brokerage firms, said rising debt supply and the weakening ability of bonds to hedge portfolio losses are increasing the risk premium investors demand from fixed income assets. Higher yields provide more interest income, but investors can still suffer substantial price losses if rates continue to rise.
The effects of renewed U.S. tightening are also spreading abroad. The Bank of Korea raised its benchmark rate twice during the summer to 3.00%, and the latest Fed increase widened the gap between U.S. and South Korean policy rates to as much as one percentage point. South Korea is one example of how changes in U.S. monetary policy can put additional pressure on central banks elsewhere.
The larger question for American investors is whether bonds can still serve as a reliable counterweight to stocks.
That could remain difficult if governments continue borrowing heavily, AI investment keeps expanding and geopolitical risks sustain inflation and interest rate uncertainty. If stocks and bonds continue moving together, investors may increasingly turn to cash, gold and other assets for diversification.
Higher interest rates also do not automatically mean lower stock valuations. Earnings expectations for the S&P 500 have continued to improve even as rates have risen, while expanding AI investment has helped support expectations for continued corporate profit growth.
Bonds now offer more income than they did during the era of near zero interest rates, but they also carry greater price risk and may provide less protection when stocks fall. Equities remain vulnerable to higher borrowing costs and rate volatility, yet strong earnings could continue to offset some of that pressure.
The bigger change in this rate cycle may therefore be not simply that borrowing costs are rising again, but that one of the most familiar relationships in American investing is becoming less dependable.
