Tokyo (東京, Tōkyō, English: /ˈtoʊkioʊ/, Japanese: [toːkʲoː] (listen)), officially Tokyo Metropolis (東京都, Tōkyō-to), is one of the 47 prefectures of Japan. It has served as the Japanese capital since 1869, its urban area housing the Emperor of Japan and the Japanese government. Tokyo forms part of the Kantō region on the southeastern side of Japan's main island, Honshu, and includes the Izu Islands and Ogasawara Islands. Tokyo was formerly named Edo when Shōgun Tokugawa Ieyasu made the city his headquarters in 1603. It became the capital after Emperor Meiji moved his seat to the city from Kyoto in 1868; at that time Edo was renamed Tokyo. The Tokyo Metropolis formed in 1943 from the merger of the former Tokyo Prefecture (東京府, Tōkyō-fu) and the city of Tokyo (東京市, Tōkyō-shi). Tokyo is often referred to as a city but is officially known and governed as a "metropolitan prefecture", which differs from and combines elements of a city and a prefecture, a characteristic unique to Tokyo. Tokyo is considered to be one of the world's most important and powerful global cities. The 23 Special Wards of Tokyo were formerly Tokyo City. On July 1, 1943, it merged with Tokyo Prefecture and became Tokyo Metropolis with an additional 26 municipalities in the western part of the prefecture, and the Izu islands and Ogasawara islands south of Tokyo. As of October 1, 2015, the population of Tokyo is estimated to be over 13.4 million, or about 11% of Japan's total population, making it Japan's most populous city. The latest estimate in 2019 shows the growing population of Tokyo with 13.9 million people, with the special wards 9.6 million, the Tama area 4.2 million, and the Islands 25,147. The prefecture is part of the world's most populous metropolitan area called the Greater Tokyo Area with over 40 million people and the world's largest urban agglomeration economy. As of 2011[update], Tokyo hosted 51 of the Fortune Global 500 companies, the highest number of any city in the world at that time. Tokyo ranked third (twice) in the International Financial Centres Development Index.[citation needed] The city is home to various television networks such as NHK,Nippon Television,TV Asahi,TBS,TV Tokyo,Fuji TV,and theTokyo MX. Tokyo ranks first in the Global Economic Power Index and third in the Global Cities Index. The GaWC's 2018 inventory classified Tokyo as an alpha+ world city – and as of 2014[update] TripAdvisor's World City Survey ranked Tokyo first in its "Best overall experience" category (the city also ranked first in the following categories: "helpfulness of locals", "nightlife", "shopping", "local public transportation" and "cleanliness of streets"). As of 2018[update] Tokyo ranked as the 2nd-most expensive city for expatriates, according to the Mercer consulting firm. and also the world's 11th-most expensive city according to the Economist Intelligence Unit's cost-of-living survey. In 2015, Tokyo was named the Most Liveable City in the world by the magazine Monocle. The Michelin Guide has awarded Tokyo by far the most Michelin stars of any city in the world. Tokyo was ranked first out of all sixty cities in the 2017 Safe Cities Index. It was also ranked the first in the 2019 safe cities index. The QS Best Student Cities ranked Tokyo as the 3rd-best city in the world to be a university student in 2016 and 2nd in 2018. Tokyo hosted the 1964 Summer Olympics, the 1979 G-7 summit, the 1986 G-7 summit, and the 1993 G-7 summit, and will host the 2020 Summer Olympics and the 2020 Summer Paralympics. Research and development in Japan and the Japanese space program are globally represented by several of Tokyo’s medical and scientific facilities, including the University of Tokyo and other universities in Tokyo, which work in collaboration with many international institutions. Especially with the United States, including NASA and the many private spaceflight companies, Tokyo universities have working relationships with all of the Ivy League institutions (including Harvard, MIT, and Yale University), along with other research universities and development laboratories, such as Stanford and the UC campuses throughout California, as well as UNM and Sandia National Laboratories in Albuquerque, New Mexico. Other partners worldwide include Oxford University in the United Kingdom, the National University of Singapore in Singapore, the University of Toronto in Canada, and Tsinghua University in China.