Long-term US government borrowing costs have hit levels not seen since 2007, with the 30-year Treasury yield trading above 5%. The trigger is a confluence of forces: the breakdown of US-Israel negotiations on Iran has pumped oil prices higher, stoking inflation fears; the national debt has crossed $40 trillion for the first time, having doubled in a decade; and the Trump administration's expansive tax and spending plans have investors questioning fiscal sustainability. Treasury Secretary Scott Bessent pledged this week to at least double Washington's purchases of long-term bonds, and staged a joint intervention with Tokyo to prop up the yen — but the relief lasted hours, not days. Yields reversed most of Bessent's Wednesday gains by Thursday. The contagion is unmistakable. UK 10-year bond rates are near their highest since 2008, with 30-year rates approaching 1998 levels. Germany's yields sit at 2011 peaks, France at a 16-year high, and Japanese borrowing costs have reached levels last seen in 1996. Every major economy is paying more to borrow because the anchor of global finance — US Treasuries — is in distress. The drivers are stacking, not substituting. The Iran war injects inflation risk through oil prices, which erodes the future value of bond payments and forces investors to demand higher yields. The $40 trillion debt pile raises questions about whether the US can service its obligations without inflating them away. New Fed Chair Kevin Warsh has abandoned the forward guidance that markets relied on, adding uncertainty. Albert Edwards of Société Générale notes the bond market is throwing a "tantrum" at the loss of the Fed's hand-holding. Japan adds a structural wrinkle. Before Washington's joint yen intervention, Tokyo had been selling US Treasury holdings to free up dollars to buy yen — pushing bond prices down and yields up from the other direction. Some analysts believe the yen intervention was less about helping Japan and more about stemming the bleeding in US bond markets from Japanese selling. The AI boom is an underappreciated accelerant. Silicon Valley's heavy borrowing to fund datacentre buildouts is flooding the bond market with corporate debt, competing with sovereign issuers for the same investor capital at a moment when appetite is already thin. The consequences cascade predictably downward. Higher yields translate directly into higher mortgage rates, loan costs, and corporate borrowing — squeezing consumers and businesses. For governments already awash in post-pandemic debt, the math is punishing: higher interest costs crowd out spending on growth, which weakens tax revenues, which widens deficits, which raises borrowing costs further. For UK Chancellor John Healey, Société Générale estimates the yield spike could erase roughly half of the £23.6 billion fiscal headroom reserved against the government's own rules. The historical parallels are uncomfortable. Edwards, known for his bearish calls, points out that French and US long bond yields are at the same levels that preceded the 2007-08 global financial crisis, while Japanese and UK yields match their 1997 Asian crisis positions. The US has long enjoyed an "exorbitant privilege" from the dollar's reserve-currency status, enabling persistent deficits. But the combination of trade disruption, fiscal excess, and geopolitical recklessness is testing whether that privilege has limits — and the bond market is answering.
