Long-term government bond yields are climbing to levels not seen in decades, as investors contend with a wave of debt issuance and growing concerns about sovereign finances as U.S. government debt is approaching $40 trillion.

Bond prices and yields move inversely, meaning yields rise when investors sell bonds. The 30-year U.S. Treasury yield has reached 5.33%, its highest level since 2007, while the equivalent U.K. gilt yield is approaching 6%. French borrowing costs are at their highest since 2008, and Japan’s long-term yields continue to set records.

TLT, the exchange-traded fund (ETF) tracking long-duration U.S. Treasuries, fell to an all-time low of $81.35 on Monday.

Oil remains a concern, as WTI crude is trading above $84 a barrel,…