The economy of Svalbard is dominated by coal mining, tourism and research. In 2007, there were 484 people working in the mining sector, 211 people working in the tourism sector and 111 people working in the education sector. The same year, mining gave a revenue of 2.008 billion kr, tourism NOK 317 million and research 142 million.[1] In 2006, the average income for economically active people was NOK 494,700, or 23% higher than on the mainland.[2] Almost all housing is owned by the various employers and institutions and rented to their employees; there are only a few privately owned houses, most of which are recreational cabins. Because of this, it is nearly impossible to live on Svalbard without working for an established institution.[3] The Spitsbergen Treaty and Svalbard Act established Svalbard as an economic free zone and demilitarized zone in 1925.[4]