traded commodities ($c = 84, 85, 27, 87, 90, 39, 29, 30, 72, 71$ according to the HS1996) in terms of total trade value (following the ranking in year 2003, [@BariFagiGarla2010]), plus $4$ commodities ($c = 10, 52, 9, 93$ according to the HS1996) which are less traded but still important for their economic relevance. The 10 most traded commodities account for $56\%$ of total world trade in 2003; moreover, they also feature the largest values of trade value per link (see table \[tab\]). Taken together, the $14$ most relevant commodities account in total for $57\%$ of world trade in 2003. As an intermediate level of aggregation between individual commodities and fully aggregate trade, we also consider the network formed by the sum of the 14 special commodities. In this way we can also draw conclusions about the robustness of our methodology with respect to different levels of aggregation.

In our analyses, we will focus on the undirected (symmetrized) representation of the network for obvious reasons of simplicity, even if the extension to the directed case is straightforward once the method in ref. [@mastrandrea2013enhanced] is appropriately generalized. In any case, several works have shown that the percentage of reciprocated interactions 