can fall from their respective rankings, as in the case of cities that have become less cosmopolitan and less internationally renowned in the current era. Characteristics Although criteria are variable and fluid, typical characteristics of world cities include: The most prominent criterion has been providing a variety of international financial services, notably in finance, insurance, real estate, banking, accountancy, and marketing; and their amalgamation of financial headquarters, a stock exchange, and other major financial institutions. Headquarters of numerous multinational corporations. Domination of the trade and economy of a large surrounding area Major manufacturing centres with port and container facilities Considerable decision-making power on a daily basis and at a global level Centres of new ideas and innovation in business, economics, and culture. Centres of digital and other media and communications for global networks Dominance of the national region with great international significance High percentage of residents employed in the services sector and information sector High-quality educational institutions, including renowned universities and research facilities; and attracting international student attendance Multi-functional infrastructure offering some of the best legal, medical, and entertainment facilities in the country High diversity in language, culture, religion, and ideologies Rankings Global city rankings are numerous, with one study suggesting as many as 300. New York City, London, Tokyo, and Paris, are notably the most prominent metropolises mentioned in this respect. They have been ranked in the top four positions in the Global Cities Index and Global Power City Index since both indices' inception in 2008, with New York and London rotating for first position over the last ten years exclusively in the top two spots. GaWC study Jon Beaverstock, Richard G. Smith, and Peter J. Taylor established the Globalization and World Cities Research Network (GaWC). A list of world cities in the GaWC Research Bulletin 5 is ranked by their connectivity through four "advanced producer services": accountancy, advertising, banking/finance, and law. The GaWC inventory identifies three levels of global cities and several sub-ranks, although the authors caution that "concern for city rankings operates against the spirit of the GaWC project" . The 2004 rankings added several new indicators while continuing to rank city-economics more heavily than political and cultural factors. The 2008 version of the list, similar to the 1998 version, is sorted into categories of Alpha world cities (with four sub-categories), Beta world cities (three sub-categories), Gamma world cities (three sub-categories), and cities with High sufficiency and