Global debt spiral threatens financial stability as yields hit two-decade highs

The world's governments are borrowing at a pace and cost not seen in nearly two decades, and the math is starting to look unsustainable. On a single Monday in early September, Japan's 10-year bond yield climbed to 2.95 percent—its highest point in three decades—while American yields pushed past 4.75 percent. Across Europe, the benchmark rates for France, Germany, Italy, Spain, and the UK have returned to levels last witnessed before the 2008 financial crisis. Australia's 10-year yield sits at its highest in fifteen years. Only China, where growth is slowing and rate cuts are expected, has seen yields move in the opposite direction.

Behind these rising yields sits a staggering accumulation of debt. The Institute of International Finance calculated that global debt has surpassed $350 trillion—equivalent to 305 percent of global GDP—with roughly $111 trillion of that owed by governments. The United States alone has seen its federal debt balloon from $26.5 trillion in 2020 to more than $40 trillion today. Since the end of 2019, governments worldwide have added approximately $100 trillion in new borrowing, much of it accumulated during the pandemic when spending exploded across every developed economy. The International Monetary Fund's figures tell a similar story: gross public sector debt has climbed from $74 trillion to more than $126 trillion in the same period.

When interest rates were near zero during the pandemic, this debt accumulation posed little immediate threat. The cost of servicing it was negligible. But as yields have risen sharply, the arithmetic has turned treacherous. The US Treasury market sits at the center of this system. The 10-year yield has climbed from less than 60 basis points in 2020 to 4.75 percent today, a shift that has rippled through every other developed economy's bond market. In Japan, government debt now exceeds 200 percent of GDP. In the United States, excluding intra-government holdings, it approaches 100 percent. Most developed economies now carry gross government debt approaching or exceeding their entire annual economic output.

Treasury Secretary Scott Bessent has suggested that economic growth is the only viable path forward, but recent geopolitical shocks have made that escape route narrower. The war in Ukraine imposed costs on Britain and Europe. The Trump administration's trade wars have disrupted global commerce. Most significantly, the decision to join Israel in attacking Iran triggered what analysts describe as the largest energy shock in history, sending oil prices upward and adding to inflation pressures. The US 10-year yield rose 81 basis points from the eve of the Middle East conflict to its current level, while developed economies' government bond yields spiked between 46 basis points in Australia and 96 basis points in France over the same period.

The Trump administration has simultaneously worsened the fiscal picture it inherited. The current term has added roughly $4 trillion to the national debt, even as the government faces a $2 trillion annual budget deficit—nearly 6 percent of GDP. Bessent has attempted limited interventions: the Treasury announced it would purchase $4 billion or more of longer-duration bonds to try capping yields and lowering borrowing costs, though in a $31.5 trillion market where roughly a third of debt matures this year and requires refinancing, such purchases appear unlikely to move the needle significantly. He has also coordinated with the Bank of Japan to defend the yen, fearing that if the Japanese currency weakens further, the roughly $1.1 trillion in Japanese money currently invested in US Treasuries could flee the market, pushing American yields even higher.

Bessent's growth strategy rests heavily on artificial intelligence investment and associated infrastructure spending. AI accounts for roughly a third of the modest 2 percent US GDP growth rate, but the sector is increasingly financed through debt, with major players competing directly with governments for investor capital. This dynamic pushes yields higher while introducing new leverage and financial interdependencies into markets already strained by sovereign debt burdens. A slowdown in AI investment would undermine Bessent's primary escape route from the debt trap without requiring a full sector collapse.

Most developed economies are running large budget deficits that show no signs of stabilizing. The compounding interest costs of their borrowings increasingly threaten to crowd out other government spending—on infrastructure, defense, social services—and potentially destabilize financial markets themselves. Some policymakers have begun discussing currency debasement and fiscal dominance as alternatives: allowing the dollar and other currencies to lose value, accepting inflation, and letting that combination transfer wealth from investors to debt issuers, thereby reducing the fiscal burden on governments. Whether Bessent can buy enough time for growth to materialize before these pressures force such choices remains the central question hanging over global markets.