Global bond yields surge as US debt concerns and geopolitical tensions drive investor anxiety

Government borrowing costs across the United Kingdom, Europe and Japan have risen to their highest levels in decades, driven by a significant sell-off in the US bond market. This turmoil reflects growing investor anxiety regarding the handling of the US economy by the Donald Trump administration and the inflationary pressures stemming from the ongoing conflict with Iran. The situation underscores the global economy’s deep dependence on US financial stability, as rising yields on American debt have dragged up borrowing costs for other major economies. Long-term US government borrowing costs have climbed to their highest point since 2007, with the 30-year Treasury bond yield trading above five per cent. This increase in yields, which represents the return investors receive for holding debt, occurs when bond prices fall due to waning demand.

In an attempt to stabilise the market, US Treasury Secretary Scott Bessent announced that Washington would at least double its purchases of long-term US bonds. This move followed a joint intervention with Tokyo earlier in the month to support the value of the Japanese yen. While Bessent’s statement initially helped to push yields down, the effect was short-lived, with rates rising again the following day and reversing much of the earlier decline. The ripple effects have been felt across the G7 nations. In the UK, 10-year bond rates are approaching their highest levels since 2008, while 30-year rates are near 1998 peaks. Germany’s borrowing costs have reached 2011 levels, and France is seeing a 16-year high. Japan is also experiencing its highest borrowing costs since 1996.

The primary driver of this investor unease is the breakdown in negotiations regarding the US-Israel war on Iran. The stop-start fighting in the Middle East has pushed up oil prices, fuelling fears over global inflation and economic growth. Compounding these concerns is the US national debt, which has hit $40tn for the first time after doubling over the past decade. Investors are increasingly wary that the administration’s tax and spending plans are unsustainable. Inflation poses a particular threat to bond investors, as it erodes the future value of money received from debt holdings, prompting them to demand higher yields to compensate for the risk. Consequently, the world’s most powerful central banks are now widely expected to raise interest rates, a challenge made more difficult by the unpredictable nature of the geopolitical conflict and the Trump administration’s policies.

Political risk further compounds the issue. In the US, there is a prevailing fear that the president has little appetite to curtail soaring borrowing and debt levels. Similar concerns are being raised regarding Britain’s prime minister, Andy Burnham, while France prepares for an election year in 2027 amid political division. Japan faces its own challenges as it increases government spending despite elevated debt levels and currency pressure. Some analysts suggest that the recent yen intervention was also driven by worries over falling Japanese demand for US Treasuries, as Tokyo had been selling US debt holdings to buy yen, which in turn pushed down bond prices and lifted yields. Additionally, the artificial intelligence boom is contributing to the pressure, as Silicon Valley companies borrow heavily to fund datacentre rollouts, requiring bond investors to absorb significant amounts of new debt.

The consequences of these rising yields are far-reaching for consumers and businesses. Higher borrowing costs will increase the price of mortgages, loans and corporate bonds, reducing spending capacity and weighing on the broader economy. Governments worldwide, already burdened by debt from recent economic shocks, are facing increased financial pressure. For the UK, analysts at Société Générale estimate that the rise in borrowing costs could eliminate about half of the £23.6bn headroom left in reserve against the government’s fiscal rules. Some experts warn of a potential doom loop where higher debt costs crowd out spending on growth-enhancing measures, locking in weak economic growth and making budget deficits more likely. While the US has historically enjoyed an exorbitant privilege due to the dollar’s status as the global reserve currency, analysts warn that current trade and fiscal policies are putting this advantage at risk. As pressure mounts ahead of the November midterm elections, investors are looking for a shift in policy, further market intervention, or reassurance from central banks to avert a potential market accident.