The discovery of North Sea oil in 1969 has made the export of oil and gas a vital part of the Norwegian economy. Norway is also the largest producer of hydroelectric power in Europe, a green energy source supplying 99 per cent of the total electricity needs of the country. The development of renewable energy and environmental technology is top priority. More than 700 businesses in the Oslo region focus exclusively on products linked to this,. The Oslo region also host a strong reserach base for this highly knowledge-intensive new industry.