The retropolation in 2010 of the 2020 zoning as functional areas

With the retropolation in 2010 of the 2020 zoning as functional areas, it is possible to analyse the evolution of the areas using constant methodological basis. This zoning corresponds to a functional approach to cities, which defines the extent of the functional area of a cluster of population and employment, in terms of the surrounding municipalities. Clusters are defined on the basis of the European density scale and very large clusters (level A) correspond to “cities”, the highest level in the density scale used by Eurostat and the OECD to make international comparisons. Municipalities which send over 15% of their workers to work in the cluster are treated as part of the functional area of the cluster. This method has been harmonised with the “Functional Urban Areas” (FUA) method advanced by Eurostat and the OECD (these are municipalities which send over 15% of their workers to work in a city). This principle of aggregation is said to be "hierarchical". The highest level clusters and their peripheries are determined first (cities, A clusters), followed by level B clusters and their peripheries, etc.

In 2010, as in 2020, more than nine in ten people live in a functional area. To analyze the evolution of zoning, three categories of areas are defined: permanent areas between 2010 and 2020, disappeared areas and new areas. In 2010, there were 702 functional areas in France outside Mayotte: 656 permanent areas (including seven cross-border areas) and 46 disappeared areas. In 2020, 42 new areas are added to the permanent areas. Two-thirds of municipalities are in the same functional area in 2010 and in 2020.

The demographic evolution of permanent areas can be decomposed into a "perimeter" effect and a "densification" effect: between 2010 and 2020, more than 90% of their demographic growth is due to a densification effect. But there are heterogeneous situations: the area of Montpellier has both expanded and become more dense, the areas of Lyon, Toulouse, Bordeaux, Nantes or Rennes have mainly become more dense (the densification effect explaining more than 80% of their demographic development) while the area of Marseille-Aix-en-Provence has mainly expanded (67% of its demographic evolution).