These maps are fascinating.
Have you ever wondered why state or county or city boundaries are drawn where they are? It turns out that administrative and government boundaries are consistent with trends in human relationships; that is, people associate most with others in the same government-defined region.
To investigate the geography of human relationships, a group of researchers has mapped human relationships in Great Britain using telephone calls as a proxy for intensity of relationship. Specifically, Ratti, et al. used total call time (scaled so as to take into account local population densities) as an indication of relationship between two people.
… we would indeed expect an agreement between the administrative boundaries and those found from human interaction, as they probably evolved together, over many centuries of mutual interplay—cohesive patterns within society promoting change in administrative boundaries and the latter, in turn, affecting human interaction.
The research was done by Carlo Ratti, Stanislav Sobolevsky, Francesco Calabrese, Clio Andris, Jonathan Reades, Mauro Martino, Rob Claxton, and Steven H. Strogatz. More information can be found here: Redrawing the Map of Great Britain from a Network of Human Interactions.