On the strength of domestic oil and gas production, last year saw the United States enjoy the greatest level of energy security since at least 1970, according to a report published Wednesday by the U.S. Chamber of Commerce’s Global Energy Institute (GEI).

In the 2020 edition of its annual Index of U.S. Energy Security Risk, the group found that, based on 37 different metrics, including geopolitical, economic, reliability, and environmental risk factors, its measure of overall domestic energy risk has declined more than 30% since 2011’s record high risk score of 100.9, to 70.1 in 2019.

The institute attributed the improvements in energy security primarily to the increase in domestic energy production from U.S. shale resources via hydraulic fracturing, horizontal drilling and...