China leads the world in total investments in renewable energy and energy efficiency, although as a percentage of overall economic activity Denmark ranks first in clean-tech spending, according to a report by the conservation group WWF. The report says that China is currently investing $65 billion a year in clean tech, with renewable energy spending growing at 77 percent a year since 2008. The U.S. spends $45 billion a year on clean technologies, with those investments growing by 28 percent a year since 2008. But Denmark, which spends $9.4 billion a year on renewable energy and energy efficiency, is the world leader when clean-tech investment is taken as a percentage of gross domestic product; Denmark’s clean-tech investments equal 3.1 percent of GDP. Using that measure, China ranks second, spending 1.4 percent of GDP on clean tech. The U.S. ranks 17th, with clean-tech investments accounting for 0.3 percent of GDP, according to the report, which gathered data on 38 countries. Measuring clean-tech spending as a percentage of GDP, the remaining countries in the top five are Germany, Brazil, and Denmark.