Stockholm had the 6th highest growth in the number of nights spent in the period 2004–2008. The largest companies in Stockholm, by number of employees (2017): Ericsson — 9,850 Södersjukhuset — 5,640 Nordea — 4,400 H&M — 4,390 SEB — 4,160 Handelsbanken — 3,000 Skanska — 2,780 Keolis — 2,650 Securitas AB — 2,250 JAG Personlig assistans — 2,060 MTR — 2,050 Postnord —2,020 Fibre-optic network The city-owned company Stokab started in 1994 to build a fibre-optic network throughout the municipality as a level playing field for all operators (City of Stockholm, 2011). Around a decade later, the network was long, making it the longest optical fibre network in the world and now has over 90 operators and 450 enterprises as customers. 2011 was the final year of a three-year project which brought fibre to 100% of public housing, meaning an extra 95,000 houses were added. (City of Stockholm, 2011) Education Research and higher education in the sciences started in Stockholm in the 18th century, with education in medicine and various research institutions such as the Stockholm Observatory. The medical education was eventually formalized in 1811 as Karolinska Institutet. KTH Royal Institute of Technology (Swedish: Kungliga Tekniska högskolan) was founded in 1827 and is Scandinavia's largest higher education institute of technology with 13,000 students. Stockholm University, founded in 1878 with university status granted in 1960, has 52,000 students . It also incorporates historical institutions, such as the Observatory, the Swedish Museum of Natural History, and the botanical garden Bergianska trädgården. The Stockholm School of Economics, founded in 1909, is one of the few private institutions of higher education in Sweden. In the fine arts, educational institutions include the Royal College of Music, which has a history going back to the conservatory founded as part of the Royal Swedish Academy of Music in 1771, the Royal University College of Fine Arts, which has a similar historical association with the Royal Swedish Academy of Arts and a foundation date of 1735, and the Swedish National Academy of Mime and Acting, which is the continuation of the school of the Royal Dramatic Theatre, once attended by Greta Garbo. Other schools include the design school Konstfack, founded in 1844, the University College of Opera (founded in 1968 but with older roots), the University College of Dance, and the Stockholms Musikpedagogiska Institut (the University College of Music Education). The Södertörn University College was founded in