They make statistical areas[0], granted they can be seen as too large to be meaningful. Rather, in this case, to determine flow, you have to use adjacency to de

They make statistical areas[0], granted they can be seen as too large to be meaningful. Rather, in this case, to determine flow, you have to use adjacency to determine "areas" of large concentration that may consist of a single county or multiple. A hard line on a county border can give inaccurate results. 0 - https://en.wikipedia.org/wiki/Statistical_area_(United_States) https://en.wikipedia.org/wiki/Statistical_area_(United_State...