For the third year in a row, Pennsylvania’s counties and municipal governments will see another drop in the annual fee revenue they receive from natural gas wells in the Marcellus shale play, according to the Associated Press.

Earlier this month, the Pennsylvania Public Utility Commission said impact fee revenue from Marcellus Shale wells dropped by almost $15 million to about $173 million in 2016. It was the third year of decline, but also the lowest annual payment in the six-year history of the impact fee.

According to the utility commission, fee revenue is declining because of an ongoing slump in natural gas prices and the increasing age of many of the wells.

Learn more: Pittsburgh Post-Gazette > Pennsylvania gas drilling fee revenue falls for third year