The 30-year Treasury yield climbed to 5.335% in secondary trading before a $22 billion auction, extending a period of elevated long-term borrowing costs not seen so persistently since the early 2000s. Auction yields have risen through 2026, from 5.046% in May to 5.058% in July and 5.216% in August, the highest in the series. Yields were trading between 5.285% and 5.335% ahead of the September sale. Recent bid-to-cover ratios, which measure demand relative to securities offered, have ranged from 2.3x to 2.7x, close to historical averages, while international and indirect buyers accounted for 65% to 80% of awards. Higher energy prices have supported inflation expectations, the large volume of Treasury issuance has increased supply, and Treasury buybacks of longer-dated debt have also affected market conditions. Strong demand at the auction could stabilize yields or push them modestly lower in the short term, while a weak result could indicate greater investor caution toward duration and trigger another selloff in long-dated bonds. Higher 10-year and 30-year Treasury yields also raise mortgage and corporate borrowing costs and can pressure equity valuations by making Treasury returns more attractive.