Chicago
Where movement communities meet racial boundaries.
Compare sharp two-group racial interfaces with communities derived from the everyday movement network.
Interactive map
Compare the ranked local Sharp Boundary Index with one estimated set of travel communities.
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Open the map full screen →Movement communities
Travel clusters derived from observed movement.
The Leiden algorithm groups Census block groups when travel is denser within a group than across it. Boundary propensity is the share of 100 runs in which each place lies on a travel-community boundary.
Sharp Boundary Index
Both groups are present, and one becomes more common as the other declines.
A gradient describes the direction and rate of local population change. The index is highest where two locally present groups change sharply in opposite directions. Each block group is assigned its highest valid score among the six White, Black, Hispanic, and Asian population pairs, ranked within Chicago.