Along with the previoustemporal aspects it isnecessary to study theirspatial aspects. Numerousspatial models have beenused to represent the spatialdistribution of a givenpopulation and its migrationsthrough a country’s networkof places.
Simultaneously, theoretical and practical studies, with dataobserved in a large number of countries, permitted theestimation of intricate parameters that are difficult to definebut easier to measure, that summarise correctly the internalmobility flows irrespective of the parcelling of the studiedterritory
This model has been re-examined recently by Martin Bell and Salut Muhidin in2011 extended to a larger number of countries in the whole world, in a chapter:Comparing internal migration between countries using Courgeau’s k (their indexk corresponds to the index kπδ of the previous formula). However these authorssay that this index has no plain language meaning. We showed with them that itis possible to link such an index to the probability for a change of residence.