Denmark has considerable sources of oil and natural gas in the North Sea and ranked as number 32 in the world among net exporters of crude oil in 2008. Denmark expects to be self-sufficient with oil until 2050. However, gas resources are expected to decline, and production may decline below consumption in 2020, making imports necessary.A large but decreasing proportion of electricity is produced from coal and nuclear energy imports, while wind turbines supply the equivalent of about 42% of electricity demand by 2015 (see Wind power in Denmark).