In 2020, annual production of associated-dissolved natural gas (or associated gas)—which is natural gas produced from oil wells—declined in the combined five major U.S. onshore crude oil-producing regions for the first time since 2016. The share of associated gas produced in these five regions (Permian, Bakken, Eagle Ford, Niobrara, and Anadarko) declined by 1.5% year over year and averaged 37.7% of natural gas production in the regions. Associated gas production averaged 14.2 billion cubic feet per day (Bcf/d) in 2020 (a 4.1% decline from 2019) amid a 9.2% drop in oil production in these regions.