Oslo is an important centre of maritime knowledge in Europe and is home to approximately 1980 companies and 8,500 employees within the maritime sector, some of which are the world’s largest shipping companies, shipbrokers, and insurance brokers. Det Norske Veritas, headquartered at Høvik outside Oslo, is one of the three major maritime classification societies in the world, with 16.5% of the world fleet to class in its register. The city’s port is the largest general cargo port in the country and its leading passenger gateway. Close to 6,000 ships dock at the Port of Oslo annually with a total of 6 million tonnes of cargo and over five million passengers. The gross domestic product of Oslo amounts to 17% of the national GDP. The metropolitan area, bar Moss and Drammen, contributed 25% of the national GDP and is responsible for more than one quarter of tax revenues. In comparison, total tax revenues from the oil and gas industry on the Norwegian Continental Shelf amounted to about 16%. Oslo is one of the most expensive cities in the world.