Some demographic crashes seen as phase transitions

The purpose of this paper is the application of a usual method of statistical mechanics—the renormalization based on Wilsonʹs recursive relations—in order to study the critical behavior of a social index, namely the live births per 1000 population. The drastic decreases of this index on certain periods have the specific features of the phase transitions as they follow approximately power laws and also, they lead to the complete change of the population age structure. The values of the critical exponents that are obtained by fitting the experimental data referring to some East European countries are in agreement with the value resulting from the theoretical approach, thus showing the universality of the power law behavior in the vicinity of the critical points, for complex social systems.