Understanding relationships across space. Attributes of places that are near to each other tend to be more similar than attributes of places that are far apart (Tobler’s First Law). The identification of spatial clusters, formal regions, distance-decay and spatial-lag effects, and autoregressive processes all display properties of spatial dependence. Understanding spatial dependence is important in the analysis of spatial interactions (such as migration, travel to work, or socializing), which tend to decline with increasing separation in predictable ways, influencing spatial choices and flows. Spatial dependence conditions the separation of activities in space, with notable impacts on the spatial organization of the economy (e.g., central services, location-allocation, functional regions, and service hinterlands).