Complex sentence: As of June 7,2017, the member states made up 30.6% of the U.S. population and 35.9% of U.S. GDP, and accounted for 18.2% of U.S. carbon dioxide emissions in 2014.
Split into simpler sentences: As of June 7,2017, the member states make up 30.6% of the U.S. population and 35.9% of U.S. GDP. They emitted 18.2% of U.S. carbon dioxide emissions in 2014.