The metropolitan scale

The growth of metropolitan areas is reshaping the urban landscape and governance around the world, producing new challenges but also opportunities for sustainable development and the management of territories. The ‘metropolitan scale’ is now internationally recognised as a key concept and perspective through which we should consider various socio-economic, spatial and political dimensions. However, our understanding of metropolitan dynamics is curtailed by a substantial lack of information at this scale. Global databases on metropolitan areas are very limited. To tackle the void, this paper employs simple definitions and heuristics to collect and present comparable data for 58 metropolises from five continents. There is a clear trade-off between the accuracy of the data and the comprehensiveness of datasets. We reflect on the experience to emphasise the obstacles that lie ahead of both scholars and policy-makers at all levels of government. A strong system of cities and metropolitan areas and the appropriate governance of these scales may provide the basis for a balanced socio-economic development – but first we will need to know more about these territories and communities. •The concept of metropolitan area is ambiguous•Many socioeconomic, spatial & political features should be considered at the metro level•We suggest simple heuristics to set metro boundaries & collect the respective data•Gathering data at the metro scale represents a first step towards governance reform•These issues are inherently political, not merely technical