Alternative explanations of hierarchical differentiation in urban systems

Cities1 always have been the locus of power and social organisation. They were also places of social and technological innovation, accompanying an increasingly complex division of labour and growing economic accumulation. In the history of societies, cities emerged at different moments on different parts of the earth, several thousand years ago, but always after agricultural techniques had been invented (about 3000 years later) and coinciding with new forms of political organisation in society (Bairoch, 1985). The maximum city size increased through history, following demographic and economic growth and technological progress. As recalled by Michael Batty in the preceding chapter, “there are always many more smaller cities than larger ones”. A less known fact is that all through historical times, as well as today in every country, in wider regions such as Europe or even in the entire world, city sizes differentiate in a surprising regular manner: the number of cities follows an inverse geometric progression in relation to their size. It is therefore not surprising if the notion of hierarchy seems almost intrinsic in urban systems, and in the two acceptations mentioned in the introduction to this book. The hierarchy of cities is a complex architecture of social relations of power or influence, inextricably mixed within a huge variety of political, economic o