Lower crude oil and natural gas prices reversed in 2019 a two-year trend of record high proved reserves in the United States as operators revised down their total proved reserves estimates, the Energy Information Administration (EIA) said on Friday.

The annual report from the EIA showed that proved reserves of crude oil and lease condensate remained basically the same in 2019 as in 2018, with a very slight increase of 0.1 percent. Proved reserves of natural gas, on the other hand, dropped by 1.9 percent, according to EIA’s data through the end of 2019.

In that year, crude oil prices were generally lower than oil prices in 2018, with the price of the U.S. benchmark, West Texas Intermediate (WTI) crude oil, averaging $57 per barrel, down by $7 a barrel compared to 2018.

“Lower crude oil prices in 2019 caused many operators to revise their total proved reserves estimates downward even though proved reserves from extensions and discoveries increased slightly,” the EIA said.

To compare, higher oil and natural gas prices in 2018 raised the proved reserves of oil and gas in the United States to new all-time highs. Oil and natural gas proved reserves beat the previous record from the previous year, when rising prices and continued shale resource development in 2017 helped push U.S. reserves to what was then record-high volumes. In 2018, U.S. proved reserves of crude oil jumped by 12 percent.

In 2019, U.S. proved reserves of oil, at 47.1 billion barrels, remain at the record level set in 2018, the EIA said in its report. Producers in Alaska added 259 million barrels of proved reserves of crude oil and lease condensate in 2019, the largest net increase in all states.

In natural gas reserves, proved reserves recorded in 2019 the first annual decrease in the United States since 2015, with Texas posting the biggest decline with drops in large shale gas areas like the Eagle Ford, Barnett, and Bossier.

Yet, total U.S. gas reserves remain at their second-highest level ever, the EIA said.