Figure 1

Purchase interactions among some of the neighborhoods in the European metropolitan area. Each neighborhood is shown as an area on the map (panel (A)) and as a node in a graph (panel (B)), and it is in both cases color-coded by its socio-economic status. Each curve in both panels represents an interaction between a pair of neighborhoods, and it is color-coded by the number of purchases made by residents of one neighborhood in another. The directions of the curves are represented by their convexity: curves of convex shape represent interactions from the left end point to the right end point, while those of concave shape represent interactions from right to left