  The concept of communicability is introduced for complex socio-economic
networks. The communicability function expresses how an impact propagates from
one place to another in the network. This function is used to define
unambiguously the concept of socio-economic community. The concept of
temperature in complex socio-economic networks is also introduced as a way of
accounting for the external stresses to which such systems are submitted. This
external stress can change dramatically the structure of the communities in a
network. We analyze here a trade network of countries exporting 'miscellaneous
manufactures of metal.' We determine the community structure of this network
showing that there are 27 communities with diverse degree of overlapping. When
only communities with less than 80% of overlap are considered we found 5
communities which are well characterized in terms of geopolitical
relationships. The analysis of external stress on these communities reveals
that several countries are very much influenced by these critical situations,
i.e., economical crisis. These weakest links are clearly identified and
represent countries that are isolated from the main trade as soon as the
external "temperature" of the system is increased. The current approach adds an
important tool for the analysis of socio-economic networks in the real-world.
