Norway’s capital, Oslo, is a relatively small city, and with fewer than 550,000 inhabitants it is home to just 12% of the country’s population. The city contributes about 17% of Norway’s GDP but one-quarter of its tax revenue. Accordingly, it is a wealthy place: as of 2008, its GDP per head was the highest in Europe. Business services provided one-fifth of Oslo’s gross value added (GVA) in 2006. The wholesale and retail trade (which accounts for 14.5% of GVA) and the financial sector (nearly 11%) are also strong. By contrast, the city’s manufacturing sector is small, accounting for less than 7% of GVA, and this is a boon to Oslo’s environment. However, the population is growing by some 2% per year, faster than any of the other Nordic capitals. Oslo is ranked third overall in the European Green City Index, with a score of 83.98 out of 100. It is also the best-performing city in terms of carbon dioxide (CO₂) emissions, largely because of the use of hydroelectricity to power rail-based public transport.