Traders have been caught by surprise by the sharp decline in U.S. government bonds since April–and this selloff has now persisted into June.

The 10-year and 30-year Treasury yields were both trading higher on the day at 4.441% and 4.972%, respectively. Higher yields mean someone somewhere is selling bonds. Yields are inversely correlated to bond prices.

The move in the 30-year has been more pronounced. It closed above 5.089% on May 21, breaking above a key 5% level that has been its cap for about two decades.