Reconstructing the world trade multiplex: the role of intensive and extensive biases

摘要

In economic and financial networks, the strength of each node has always animportant economic meaning, such as the size of supply and demand, import andexport, or financial exposure. Constructing null models of networks matchingthe observed strengths of all nodes is crucial in order to either detectinteresting deviations of an empirical network from economically meaningfulbenchmarks or reconstruct the most likely structure of an economic network whenthe latter is unknown. However, several studies have proved that real economicnetworks and multiplexes are topologically very different from configurationsinferred only from node strengths. Here we provide a detailed analysis of theWorld Trade Multiplex by comparing it to an enhanced null model thatsimultaneously reproduces the strength and the degree of each node. We studyseveral temporal snapshots and almost one hundred layers (commodity classes) ofthe multiplex and find that the observed properties are systematically wellreproduced by our model. Our formalism allows us to introduce the (static)concept of extensive and intensive bias, defined as a measurable tendency ofthe network to prefer either the formation of extra links or the reinforcementof link weights, with respect to a reference case where only strengths areenforced. Our findings complement the existing economic literature on (dynamic)intensive and extensive trade margins. More in general, they show thatreal-world multiplexes can be strongly shaped by layer-specific localconstraints.