A city that has a substantial, straightforward effect on world affairs: economically, socially, and politically. Key descriptors include: centrality—a concentration of international activities; externality—a relatively high global role, compared to its national role; and connectivity—as measured by the numbers and intensity of transactions. ‘World cities are not merely outcomes of a global economic machine; rather, they are key structures of the world economy itself’ (Taylor et al. (2002) Urb. Studs 39, 13; see also P. Taylor 2003). Gugler (2003) Int. J. Urb. & Reg. Res. 27, 3 notes that world cities in the developing world are more subject to the economic, political, and cultural impact of powerful foreign actors: governments, corporations, international organizations, universities, the media. The resources they can draw on are much more limited, even as they have to make heavier investments in infrastructure to meet the standards required by foreign investors. Beaverstock et al. (1999) Cities 16, 6 propose a hierarchy of world cities: ‘alpha world cities’, such as London, New York, and Frankfurt; ‘beta world cities’, such as Zurich, São Paulo, and Mexico City; and ‘gamma world cities’ such as Buenos Aires, Montreal, and Santiago. Ewers (2007, Geog. J. 68, 2–3) also examines measurement issues and the methodological problems in creating indices of world cities. See Brown et al. (2007) GaWC Research Bulletin 236 on world city networks, and Ewers (loc. cit.) on the role played by world cities in global migrations. Smith (2003, PHG 27, 1) holds that further progress in the study of world cities and their networks can be made through actor-network theory and non-representational theory. See Taylor (2007) GaWC Res. Bull. 238 for an admirably clear summary of GaWC’s work on world cities.

http://www.lboro.ac.uk/gawc/citylist.html GaWC Inventory of World Cities.