Dispersion of measurements in demography: a historical view

This paper traces the development of the notions of dispersion, in demography and in probability, distinguishing two main meanings for this term: the one first, to scatter, to cast here and there; in second, to separate the elements, to break the unity of a set. This development was initiated by the work of Pascal and Fermat for probability and Graunt for political arithmetic, during the second half of the seventeenth century. Major progress was made with the probabilistic and demographic work of Laplace, who developed an epistemic approach of these two notions of dispersion. However, with an objectivist probabilistic approach, that took place in the middle of the nineteenth century, and the use of population censuses, these notions entirely disappeared from the demographic field. In the early 1980’s the development of event history analysis and of multilevel analysis permitted the reintroduction of these two notions.