After seven years of dramatic increases, proved reserves of natural gas declined 6.5 percent in Pennsylvania from 2014 to 2015, from 60.4 trillion cubic feet to 56.5 trillion cubic feet, the U.S. Energy Information Administration says.

The decline in proved gas and oil reserves reflects a steep reduction in fossil-fuel prices, which makes some reserves uneconomic to produce. Nationwide, proved gas reserves declined by 16.6 percent, and proved oil reserves declined by 11.8 percent from 2014 to 2015, according to an EIA report released Wednesday.

After the development of shale-gas production, proved reserves of natural gas surged nearly 17 times in Pennsylvania, from 3.6 trillion cubic feet, from 2007 to 2014. Pennsylvania is now the second largest gas-producing state, behind Texas.

The decrease in proved reserves has had a profound impact on the balance sheets of oil and gas producers, which report the value of their reserves to investors.