A group of network analysts wondered whether national boundaries really reflect people's connections to each other. So they looked at links formed between people phoning each other in Great Britain, and discovered which regions really have the most in common.

Here you can see a map that's the result of the first phase in their research, where they looked at the strongest 80 percent of links between people, which they measured in "total talk time between areas within Britain." The researchers explain, "The opacity of each link is proportional to the total call time between two areas." The colors represent regions of tightly-connected people, which map remarkably well to geographical spaces.

The researchers explain their work today in PLoS One:

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.

Above you can see the "core areas" the researchers identified as having citizens with the tightest relationships with one another, based on number and length of phone calls. Core areas are in solid colors, and you can contrast these with the UK government's own regional boundaries - drawn in black. So the traditional, state-mandated regions of the UK don't always map very well to people's actual connectedness to one another.

Read the full article at PLoS One