CNN  —  A key US inflation gauge rose last month to its highest level since April 2023. The Producer Price Index, a closely watched measure of inflation at the wholesale level, rose 2.1% for the 12 months ended in March, according to Bureau of Labor Statistics data released Thursday. The increase from a 1.6% annual gain in February was lower than expectations. The acceleration in the prices producers pay for goods and services highlights the persistence of inflation, the bumpy path to bring it lower, and supports fears that interest rates will stay higher for longer. On a monthly basis, US wholesale prices rose 0.2%, markedly slower than the 0.6% gain in February.