THE world’s trade network is organised in a completely different way from the internet, electricity grids and networks of friends. According to Diego Garlaschelli and Maria Loffredo of the University of Siena in Italy, all the structural properties of the trade network are determined by a single parameter: the wealth of each country.
The internet and most other well-studied networks form by growing gradually, say when a new website links to websites that are already well connected. The result is usually a scale-free network, where most nodes have only a few links, but a hierarchy of better-connected nodes with a…
