The total U.S. energy security risk fell 1.6 points (2%) to 75.8 in 2018, its fourth-lowest point since 1970, and the lowest since 1995, thanks in large part to the nation’s robust shale plays, according to the U.S. Chamber of Commerce Global Energy Institute (GEI).

The 88-page report, which was released Tuesday, reveals some of the best results in GEI’s 10 years analyzing the state of America’s energy security.

“Our index has documented the incredible story of how the shale energy revolution has ensured America’s energy security,” said GEI President Marty Durbin. “Our nation’s diverse energy sources, including coal, renewables and nuclear, add to that energy security and make the U.S. the largest energy producer in the world. This benefits our economy, our global security and the environment, as America’s energy production is held to the world’s highest environmental standards.”

The index employs 37 energy security metrics measuring geopolitical, economic, reliability and environmental risks, covering the period 1970-2040 and incorporating the latest historical data and forecast models. A lower score indicates a lower level of risk.

Most major metrics held relatively steady in this year’s edition, GEI said, with significant improvements in crude oil price volatility, security of petroleum imports (since imports have decreased), and oil and natural gas import expenditures.

“Greater domestic unconventional oil and natural gas production from shale formations occurring against a backdrop of an increasingly efficient economy have been the biggest factors contributing to the improved U.S. energy security picture since 2011.”

The highest risk year was 2011 at 101.4 and the best-ever score of 75 was 1992.