Renewable energy sources averaged about 21% of primary energy supply and 38% of electricity generation in 2009 (Figure 5.1), far above the OECD Europe average (10.5% and 23%, respectively). Hydropower has long been the major domestic source of electricity. However, hydropower generation is subject to large annual variations linked to rainfall levels, which have caused major fluctuations in overall energy supply and carbon dioxide (CO2) emissions.