We live in an age of 'list-mania'; there is so much information available that ordering selected topics has become popular entertainment. And so it is with cities, there are numerous rankings of cities available in both the commercial and academic spheres. People are interested in where their city ranks and this can be fun. Some years ago my city, Newcastle, was ranked above Rio as a 'world party city'; it made headlines in the local press. But beyond boosterism there has been a genuine concern

more »

... for cities as business centres in a rapidly globalizing world economy. GaWC, with its measures of network connectivity, has contributed to this situation with its rankings of the importance of cities in the world city network. In fact, it appears that it is these rankings that most people want from GaWC. But there is a basic sense in which concern for city rankings operates against the spirit of the GaWC project (Taylor 2004). City rankings fit into the approach to inter-city relations that emphasizes competition between cities. This is in keeping with the long-term, conventional theoretical approach to inter-city relations that described 'national urban systems' in each of which exists a 'national city hierarchy' broadly conforming to classical central place theory. The intellectual power of this theoretical framework can be appreciated through the fact that 'city hierarchies' appear almost natural (Taylor 2009) -how else would cities relate to each other except through hierarchies? From this position ambitious cities are expected to 'climb the hierarchy' at the expense of rival cities. But there is an alternative position. I think that inter-city relations are inherently cooperative; cities exist in city networks and networks can only exist through collective complementarities (Powell 1990; Thompson 2003) . Cities need one another, they grow through relations with one another not by eliminating one another in a world of city competition. Thus one of GaWC's aims has been to reposition research on inter-city relations from the easy seduction of hierarchies to the complex subtleties of networks. Of course, in practice, inter-city relations are both cooperative and competitive; it is a matter of where to begin. At GaWC we start with network so that we measure a 'world city network with hierarchical tendencies' (Taylor 2004) . We treat network relations as generic to cities and hierarchical relations as contingent: city competitiveness varies in space and time with competitive relations being stronger locally and in cyclical downturns. Returning to theory, our starting point is the specification of a world city network to replace hierarchical theory in its various forms .