The evolving structure of global trade

The evolving structure of global trade. To a significant extent, the cells, tissues, organs, and so forth that make up a living organism act independently as they perform their interrelated tasks. According to spin-glass models of evolution, modular structures analogous to those in biological systems generically arise for systems in changing environments. Moreover, such structures help ensure that a system is better able to cope with changes to come. Now Michael Deem of Rice University and his student Jiankui He have applied those conclusions to global trade. To do so, they came up with a parameter—the cophenetic correlation coefficient—that quantifies the modularity of the global trade network. As the figure shows, the system becomes more modular (the CCC increases) in response to environmental change—in this case, global recession. (The red bars indicate more severe recessions; the green bars, less severe. Data for the 2008 recession were not available.) But the...