Bond yields have risen across the United States, Japan and Europe, reviving concern that debt accumulated during the near-zero-rate era will become more costly to refinance. U.S. Treasury volatility surged on Sept. 24, 2026, as the ICE BofA MOVE Index reached 104.58 and the 10-year yield briefly hit 5.2%; the yield had reached 5.23% on Friday, its highest level since 2007 and more than a full percentage point above its level before the Iran war started. The 30-year yield reached 5.49%, its highest since 2004. Japan's 10-year yield breached 3%, its highest since 1996, while Germany and the U.K. reached their highest 10-year yields since 2009. Hawkish Federal Reserve comments and weak demand at Treasury auctions added pressure to bonds. Higher oil prices linked to the Middle East conflict, strong economic activity, wider fiscal deficits and heavy AI investment are also increasing borrowing costs. JPMorgan Chase estimates $4.1 trillion in AI-related debt will be issued through 2030, while the CBO projects about $1 trillion in U.S. net interest outlays this year and the IMF projects global public debt will reach 100% of GDP by 2029. Despite the bond-market pressure, optimism surrounding artificial intelligence and easing Middle East supply concerns supported U.S. mega-cap stocks.