the WTW, binary constraints must therefore be added to the weighted ones. Economically, this suggests that additional higher-order mechanisms besides those accounting for the joint evolution of degrees and strengths are not really necessary in order to explain the structure and dynamics of the WTW. On the other hand, we also show that degrees and strengths are ‘irreducible’ to each other, i.e. any minimal macroeconomic model aiming at reproducing the WTW should not discard any of the two quantities.

Our work complements the existing economic literature about the so-called *extensive* and *intensive margins* of trade [@ricardo1819principles; @felbermayr2006exploring; @DeBene_Tajoli_2011], defined as the preference for the network to evolve by establishing new connections or by strengthening the intensity of existing ones respectively. While extensive and intensive margins are traditionally defined at an intrinsically dynamical level, we define the new concept of *extensive and intensive biases* as a purely static notion, and for each pair of countries separately. We focus on cross-sectional data and evaluate whether, at a given point in time, pairs of countries are ‘shifted’ along the intensive or extensive direction as compared to an appropriate null model. Thus, our methodology does *not* establish whether the WTW proceeds along the extensive 