Spatial agglomeration is a central aspect of human life and of the geographic space in which most economic and social exchanges take place (Bairoch 1988). The size and shape of this geographic space have key implications for policy design, as they affect the regular patterns of mobility and interactions of people, goods, and ideas. This functional reality is weakly captured by the usual political-administrative units. Functional territories, as we call them in this study, represent a complex socio-spatial picture of overlapping markets between "areas or locational entities which have more interaction or connection with each other than with outside areas" (Brown and Holmes 1971, p 57), and with high frequency of economic and social interactions between their inhabitants, organizations, and firms (Berdegué et al. 2011).

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