To determine the most eco-friendly states, 24/7 Wall St. created an index of measures of energy use and pollution. States ranked as more eco-friendly if a larger share of electricity generated in the state comes from renewable sources, if the state has a relatively strict set of policies related to energy efficiency, if air pollution levels are relatively low, and if a relatively high share of jobs are in industries determined to be green. States were penalized for having a high share of total electricity generation from oil, coal, or natural gas combustion.
Average daily density of fine particulate matter is measured in micrograms per cubic meter and is from County Health Rankings & Roadmaps, a Robert Wood Johnson Foundation and University of Wisconsin Population Health Institute joint program, and is for 2014. Electricity generation by source is for 2017 and comes from the U.S. Energy Information Administration.
The share of jobs in green industry employment by state comes from the U.S. Bureau of Labor Statistics’ Quarterly Census of Employment and Wages, and is for 2017.
Each state’s energy efficiency policy score rank in the index came from the American Council for an Energy-Efficient Economy’s 2018 State Energy Efficiency Scorecard, which measures state and regional policy on transportation, utility, buildings, and other energy efficiency standards.