Investors are selling off bonds from the U.S. government, as part of a trade known as “Sell America.”

The United States government has had to pay more to borrow in the global debt markets. On Wednesday, the Treasury department found that there was tepid demand for an auction for $20 billion worth of bonds, and ended up paying a slightly higher interest rate (or yield) than expected.

This has spooked markets. Yields on 30-year U.S. Treasuries have spiked above 5% this week — an unusual, and unsettling, surge in the price that the U.S. government pays on its long-term debt. An increase in bond yields is particularly damaging to the economy because it jacks up the interest rates on many things that consumers pay, such as on mortgages and other loans.