Territorial population change is the result of natural change and migration, with the first primarily affecting national populations, and the second local populations. At local level, migration patterns depend largely upon housing or, more specifically, on changes in the number of primary residences and in their occupancy.
Hence, the depopulation of Paris “intra muros” since the Second World War can be explained by a decline in the number of primary residences—despite an increase in the number of dwellings—and, above all, a decrease in household size which, like elsewhere in France and the Western world, reflects the “couple crisis” and demographic ageing, but equally the appeal of Paris for singles and small households and the “banishment” of families to the suburbs.
This pattern of urban residence can be explained by several factors, above all by the size of dwellings – small in Paris and larger in the suburbs – and their higher cost inside Paris than beyond the city limits. These factors are raising the proportion of young adults and of professionals and higher-level occupations in the Parisian population. This trend is especially pronounced in the central districts, where the small dwellings and animated social life are particularly attractive to the singles population.