Mapping Shifting Hierarchical and Regional Tendencies in an Urban Network through Alluvial Diagrams

We employ alluvial diagrams to map the evolution of interweaving hierarchical and regional tendencies in the transnational urban networks created by globalizing producer services firms. We first applied a hierarchical cluster analysis to 139 leading cities for 2000, 2004 and 2010 respectively, whereby cities are grouped based on their portfolio of firms. In the alluvial diagram, individual blocks represent city clusters, and in each year blocks are ranked hierarchically (i.e. from top to bottom based on the average number of firms per member city). Clusters are named after the formative type of member city, e.g. the continued presence of hierarchically ordered and regionally coherent clusters of United States cities. Horizontal streams connect preceding and succeeding clusters based on shared city membership, which allows tracing how individual as well as groups of cities’ positions evolve over time. The width of a streamline is proportional to the number of cities with the corresponding membership change.

  • Red: Overall, Chinese cities are becoming more important in the networks of globalized producer services firms. Shanghai and Beijing join Hong Kong in a cluster of leading cities trailing NY-LON (New York and London), whereas Taipei retains its position in a cluster of second-ranked cities. The stream in the lower half of the diagram represents the trajectory of Guangzhou, which is also becoming more important over time, and has come to form a cohesive regional group with Ho Chi Min and Hanoi around the Gulf of Tonkin.
  • Green: The primary Indian cities (Mumbai and New Delhi) join a cluster of major second-ranked cities, while the other Indian cities rise from the group of peripheral cities to form a cluster of their own.
  • Purple: Moscow and Sao Paulo equally become more important in the networks of globalized producer services firms over time.
  • Yellow: Istanbul and Dubai are (increasingly) the two leading cities in the region. A regional group of Gulf cities (Manama, Abu Dhabi, Riyadh) emerges from the group of peripheral cities.
  • Members of selected clusters in 2010:¬†Global I: Beijing, Hong Kong, Paris, Shanghai, Singapore, and Tokyo.¬†Global II: Brussels, Dubai, Frankfurt, Madrid, Milan, Moscow, and Sao Paulo.

The black/white version of this picture is accepted as a featured graphic in Environment and Planning A.

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