Silicon Valley is a region in the southern part of the San Francisco Bay Area in Northern California that serves as a global center for high technology, innovation and social media. It corresponds roughly to the geographical Santa Clara Valley. San Jose is the Valley's largest city, the third largest in California, and the tenth largest in the United States. Other major Silicon Valley cities include Palo Alto, Menlo Park, Cupertino, Santa Clara, Mountain View, and Sunnyvale. The San Jose Metropolitan Area has the third highest GDP per capita in the world (after Zurich, Switzerland and Oslo, Norway), according to the Brookings Institution.The word "silicon" in the name originally referred to the large number of silicon chip innovators and manufacturers in the region, but the area is now the home to many of the world's largest high-tech corporations, including the headquarters of 39 businesses in the Fortune 1000, and thousands of startup companies. Silicon Valley also accounts for one-third of all of the venture capital investment in the United States, which has helped it to become a leading hub and startup ecosystem for high-tech innovation and scientific development. It was in the Valley that the silicon-based integrated circuit, the microprocessor, and the microcomputer, among other technologies, were developed. As of 2013, the region employed about a quarter of a million information technology workers.As more high-tech companies were established across San Jose and the Santa Clara Valley, and then north towards the Bay Area's two other major cities, San Francisco and Oakland, the "Silicon Valley" has come to have two definitions: a geographic one, referring to Santa Clara County, and a metonymical one, referring to all high-tech businesses in the Bay Area. The term is now generally used as a synecdoche for the American high-technology economic sector. The name also became a global synonym for leading high-tech research and enterprises, and thus inspired similar named locations, as well as research parks and technology centers with a comparable structure all around the world.