Yields on short-term debt of the United States government turned negative on Wednesday.

Three-month Treasury yields fell to negative 0.035. One month Treasury yields were negative as well.

Bond yields fall when investors bid up the prices of the bonds. A negative yield means that the bond is priced high enough over its face value that the interest the bond will pay over its remaining lifetime is less than the premium paid.

This does not mean the people buying the bonds today will lose money. If bond prices continue to rise, those holding the bonds now will be able to sell them for a profit later.

Tens of trillions of dollars of bonds, mostly government debt, have negative yields. In the U.S. yields have mostly remained positive, in part because the Federal Reserve has said it does not want to push its target into negative territory. President Donald Trump, however, has frequently pointed to negative rates abroad and argued that the U.S. rates should be lower than those of other countries.