Government borrowing costs worldwide are climbing as investors demand greater compensation for holding longer-dated debt. The surge in U.S. Treasury yields has even prompted Treasury Secretary Bessent to announce an expansion of long-term bond buybacks, but this intervention failed to stop the 10-year Treasury yield from breaking above 5%, a level not seen in nearly two decades. A host of factors explain why investors are retreating from long-term sovereign debt, including concerns over widening fiscal deficits, persistently elevated inflation fueled by trade wars and Middle East conflicts, and a wave of corporate borrowing by tech giants building artificial intelligence (AI) infrastructure that has siphoned off funds that might otherwise flow into bonds. While the Fed's September rate hike eased concerns about the central bank's commitment to fighting inflation, the structural forces driving the bond sell-off remain intact, keeping yields elevated. The average yield on bonds issued by Group of Seven (G-7) members is currently at its highest level since 2000.

What makes long-term bonds so distinctive? Government bonds from wealthy nations are widely regarded as the world's safest securities, given the high likelihood of repayment. Governments typically lock in financing costs over extended periods, such as 30 years, and some even issue bonds with maturities stretching to 100 years. But that does not mean these instruments are risk-free for investors. If inflation and short-term interest rates climb, the real value of bond coupons is eroded, and the principal repaid at maturity also loses purchasing power. The longer the maturity, the more prolonged the exposure to inflation. This is precisely why long-term bonds are more sensitive to rising rates and inflation, and why they have become the epicenter of the recent sell-off. In mid-September, the 30-year U.S. Treasury yield reached its highest level since 2007, Japan's 30-year yield neared historic highs, and UK gilt yields hit their highest point since 1998.

Why aren't investors snapping up high-yielding long-term bonds? In theory, they should, but the supply-demand dynamics of the bond market are undergoing structural shifts. For much of the past two decades, global savings were abundant, particularly in Asia, with a glut of capital chasing relatively scarce safe assets, helping to suppress long-term real yields. Then-Fed Chair Alan Greenspan once described persistently low long-term yields as a "conundrum," noting that long-term rates remained subdued even as the Fed raised short-term borrowing costs. Today, governments worldwide are ramping up spending across areas ranging from renewable energy to defense. The U.S. needs to borrow more to service a national debt exceeding $40 trillion and cover annual fiscal shortfalls, which the Congressional Budget Office estimated in August would reach $2.1 trillion. Trump has proposed issuing a $5,000 "dividend" to every adult American citizen if Republicans retain control of Congress after the November midterms, which could further inflate government borrowing.

While the global supply of government bonds surges, foreign investor demand is weakening, and central banks are reducing their bond holdings after years of buying, further dampening demand. European Central Bank Executive Board member Isabel Schnabel has characterized this shift as moving from an "era of savings glut" to one of "bond glut." This implies an investor base that is more price-sensitive, with private buyers typically demanding higher compensation to hold long-term bonds. Structural changes in pension systems and retirement structures have also diminished the ranks of traditional long-term buyers.

What premium are investors demanding for long-term bonds? A model developed by Bloomberg Economics shows that the term premium on U.S. long-term bonds has risen by more than 3 percentage points from its low during the pandemic. U.S. Treasuries have traditionally enjoyed a "convenience yield," meaning investors are willing to pay a premium and accept lower returns due to their high liquidity, safety, and usability as collateral. Some argue this privilege has been eroded as the U.S. debt stock balloons and Trump's policy-making appears increasingly erratic. Others contend such concerns are overstated, insisting Treasuries remain the safest debt asset class.

Why are long-term yields so crucial to the economy? A disorderly bond market sell-off can spell trouble for governments reliant on debt markets to finance fiscal deficits. The UK knows this all too well, as seen in the downfall of Prime Minister Liz Truss in 2022. Bessent remarked earlier this year that bond markets have "toppled more governments than cannons." Long-term bond yields serve as the pricing benchmark for a range of consumer loans, including mortgages, and corporate debt. With inflation having made living costs less affordable over the years, rising bond yields could further strain household borrowing costs. Savers, however, stand to benefit. The transmission from bond yields to consumer debt markets is not always straightforward. In the U.S., the 30-year mortgage rate is more closely tied to the 10-year Treasury yield than to the 30-year yield, because homeowners typically pay off or refinance their mortgages within a timeframe closer to 10 years.

What measures can governments take to counter rising long-term yields? Many governments are adjusting their borrowing plans by shifting toward shorter-dated issuance. While short-end yields are currently lower, these bonds have shorter maturities, requiring governments to refinance more frequently, potentially at higher rates. The Bank of England decided to halt sales of long-term bonds from its portfolio to ease market pressure, while the U.S. has taken a different approach. The Treasury announced in August that it would expand buybacks of 10- to 30-year Treasuries, aiming to ease what Bessent described as "fever" in the market. But the initial buyback size fell short of expectations, and yields subsequently climbed to multi-year highs, with rising oil prices also a contributing factor. Fundamentally, governments need to convince investors they can control inflation and fiscal deficits. This may require a mix of tax increases and spending cuts, measures that are likely to be unpopular with voters.

Should investors be worried about surging yields? To some extent, rising yields are good news for bondholders. With equities hovering near record highs, higher yields reflect a resilient global economy capable of absorbing higher borrowing costs. After the global financial crisis, bond yields were near zero due to dismal growth prospects. The recent yield increase can also be viewed as a normalization toward pre-crisis levels. The 10-year Treasury yield currently stands at 4.95%, slightly above its 40-year average. As Wells Fargo economists Tom Porcelli and Michael Pugliese wrote in an August research note: "People like to use the phrase 'higher for longer.' We think a more accurate description is 'normal for longer.'"