The United States is the world's largest energy consumer. The majority of this energy is derived from fossil fuels. America accounts for a quarter of the world's oil consumption. In 2007, about 58% of the petroleum used in the Unites States was imported from foreign countries. The top five exporters of oil to America were Canada, Saudia Arabia, Venezuela, Mexico, and Nigeria. With skyrocketing oil prices negatively impacting the U.S. economy and a dependence on foreign oil posing a threat to national security, the United States is pursuing viable alternatives to oil imports. These include increasing domestic drilling for oil and natural gas, nuclear power and renewable sources.