  We study the topological properties of the multinetwork of commodity-specific
trade relations among world countries over the 1992-2003 period, comparing them
with those of the aggregate-trade network, known in the literature as the
international-trade network (ITN). We show that link-weight distributions of
commodity-specific networks are extremely heterogeneous and (quasi) log
normality of aggregate link-weight distribution is generated as a sheer outcome
of aggregation. Commodity-specific networks also display average connectivity,
clustering, and centrality levels very different from their aggregate
counterpart. We also find that ITN complete connectivity is mainly achieved
through the presence of many weak links that keep commodity-specific networks
together and that the correlation structure existing between topological
statistics within each single network is fairly robust and mimics that of the
aggregate network. Finally, we employ cross-commodity correlations between link
weights to build hierarchies of commodities. Our results suggest that on the
top of a relatively time-invariant ``intrinsic" taxonomy (based on inherent
between-commodity similarities), the roles played by different commodities in
the ITN have become more and more dissimilar, possibly as the result of an
increased trade specialization. Our approach is general and can be used to
characterize any multinetwork emerging as a nontrivial aggregation of several
interdependent layers.
