In 2007, Iceland was the seventh-most productive country in the world per capita (US$54,858), and the fifth-most productive by GDP at purchasing power parity ($40,112). About 85 per cent of total primary energy supply in Iceland is derived from domestically produced renewable energy sources. Use of abundant hydroelectric and geothermal power has made Iceland the world's largest electricity producer per capita. As a result of its commitment to renewable energy, the 2016 Global Green Economy Index ranked Iceland among the top 10 greenest economies in the world. Historically, Iceland's economy depended heavily on fishing, which still provides 40% of export earnings and employs 7% of the work force. The economy is vulnerable to declining fish stocks and to falls in world prices for its main material exports: fish and fish products, aluminium, and ferrosilicon. Whaling in Iceland has been historically significant. Iceland still relies heavily on fishing, but its importance is diminishing from an export share of 90% in the 1960s to 40% in 2006.