Hierarchy in social organization

We find that area and population distributions of nations follow an inverse power-law, as is known for cities, but with a different exponent. To interpret this result, we develop a growth model based on the geometrical properties of partitioning of the plane. The substantial agreement between the model and the actual nation distributions motivates the hypothesis that the distribution of aggregates of organisms is related to land partitioning. To test this hypothesis we follow the development of bacterial colonies of Escherichia coli, which, compared to humans, are on a completely different level of complexity. We find that the distributions of E coli colonies follow an inverse power law with exponent similar to that of nations. (C) 2003 Elsevier B.V. All rights reserved.