Fig. 2: Hierarchical stratification of movement categories by industry sector.

a Toy illustration for the hierarchical stratification of a mobility network into network layers that encode different behavioral categories of movements, defined using the North American Industry Classification System (NAICS). The number of digits in a NAICS code determines the hierarchy depth (i.e., level of coarseness when refining movement categories into subcategories). b A map of census tracts in Harris County (bottom) overlaid by three example networks at three different coarseness levels: all movements (top), health care and social assistance (middle), and hospitals (lower). c Fraction of POIs in each NAICS category for Harris County (left) and fraction of total observed movements in each NAICS category (right). In both panels, for each category, different coloration indicates finer subcategories. See Fig. 4 and Supplementary Fig. 1 for additional details about the stratification of categories into subcategories and their industry sector NAICS codes.