$C=97$ possible commodities listed according to the Harmonized System 1996 (HS1996 [^2]). For each year $t$ ($1\le t\le T$) and each commodity $c$ ($1\le c\le C$), the starting data are represented as a matrix whose elements are the trade flows directed from each country to all other countries [^3]. The matrix elements specifying the multiplex are denoted by $e^{(c)}_{ij}(t)$, where $e^{(c)}_{ij}(t)> 0$ whenever there is an export of good $c$ from country $i$ to country $j$, and $e^{(c)}_{ij}(t)= 0$ otherwise. Rows and columns stand for exporting and importing countries respectively. The value of $e^{(c)}_{ij}(t)$ is in current U.S. dollars (USD) for all commodities.

Given the commodity-specific (multiplex) data $e_{ij}^{(c)}(t)$, we can compute the total (aggregate) value of exports $e_{ij}^{AGG}(t)$ from country $i$ to country $j$ summing up over the exports of all $C=97$ commodity classes: $$e_{ij}^{AGG}(t)\equiv \sum_{c=1}^C e_{ij}^{(c)}(t)$$ The particular aggregation procedure described above, introduced in [@BariFagiGarla2010], allows us to compare the analysis of the $C$ commodity-specific layers of the multiplex with a [$(C+1)$-th]{} aggregate network, avoiding possible inconsistencies between the original aggregated and disaggregated trade data.

We put special emphasis on the $14$ particularly relevant commodities identified in [@BariFagiGarla2010] and reported in table \[tab\]. They include the $10$ most 