In other words, these maps show how the borders of countries and counties could be redrawn if they were to reflect communities rather than governmental regions.

The geography of talk in Great Britain. This figure shows the strongest 80% of links, as measured by total talk time, between areas within Britain. The opacity of each link is proportional to the total call time between two areas and the different colours represent regions identified using network modularity optimisation analysis.

The core regions of Britain. By combining the output from several modularity optimization methods we obtain the results shown in this figure. The thick black boundary lines show the official Government Office Regions partitioning together with Scotland and Wales. The black background spots show Britain’s towns and cities, some of which are highlighted with a label.

via Redrawing the Map of Great Britain from a Network of Human Interactions – plosone.org (CC BY 2.5)

Abstract

Do regional boundaries defined by governments respect the more natural ways that people interact across space? This paper proposes a novel, fine-grained approach to regional delineation, based on analyzing networks of billions of individual human transactions. Given a geographical area and some measure of the strength of links between its inhabitants, we show how to partition the area into smaller, non-overlapping regions while minimizing the disruption to each person’s links. We tested our method on the largest non-Internet human network, inferred from a large telecommunications database in Great Britain. Our partitioning algorithm yields geographically cohesive regions that correspond remarkably well with administrative regions, while unveiling unexpected spatial structures that had previously only been hypothesized in the literature. We also quantify the effects of partitioning, showing for instance that the effects of a possible secession of Wales from Great Britain would be twice as disruptive for the human network than that of Scotland.

The most dramatic example of a community not contained within its borders is Wales, which is pretty neatly sliced into north, mid and south.

It would be interesting to see a map like this redrawn with internet and postal communications.