The 2015 edition of the Sustainable Energy in America Factbook found that “over the 2007-2014 period, U.S. carbon emissions from the energy sector dropped 9%, U.S. natural gas production rose 25% and total U.S. investment in clean energy (renewables and advanced grid, storage and electrified transport technologies) reached $386 billion”. The report was commissioned by the Business Council for Sustainable Energy and prepared by analysts at Bloomberg New Energy Finance. On February 2, the 2013 Renewable Energy Data Book was released by the National Renewable Energy Laboratory (NREL) on behalf of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy. Key findings include: Renewable electricity, including hydropower and biopower, grew to nearly 15% of total installed capacity and 13% of total electricity generation in the United States in 2013, compared to 23% of all electricity generation worldwide, and 15% in the UK. Solar electricity was the fastest growing electricity generation technology in the U.S., with cumulative installed capacity increasing by nearly 66% from the previous year.