1This work is a set of studies by Alfred Dittgen on relations between population trends and housing at the local scale. Dittgen began studying local populations in 1985. Here he focuses on population developments in Paris and the suburb of Marne-la-Vallée.
2Dittgen is interested in the nature and impact of the housing factor in analysing local demographic dynamics and making population projections. Therein lies all the value and complexity of the local approach to demographic study.
3In the first and most substantial section, he describes the connection between local populations and housing stock. He first examines population trends in Paris in the second half of the twentieth century. Population movement, directly conditioned by housing stock structure, modified the structure of the Paris population at that time: there were over twice as many entries as births, and over four and a half times as many departures as deaths.
4In many western countries, the generations are less and less inclined to cohabit, and housing stock affects local population size and characteristics. In theory, an increase in number of housing units results in an increase in the population, but what is regularly observed is stability, for two reasons: first, the proportion of units available for permanent occupants (main residence) may fall as the proportion of second or occasional residences rises; second, household size may fall. In practice, then, some areas actually see a fall in inhabitant numbers despite an increase in housing units.
5Household and household-member typologies are directly related to the size and occupancy status of available housing. Unit size impacts on household size but also on resident age and sex structure: large units usually receive families with children whereas smaller ones are more likely to be occupied by single persons or childless couples.
6Housing occupancy status may be reflected in the proportion of residents belonging to a given socio-occupational category. Alfred Dittgen’s findings show that the different types of units (for first homebuyers; private-sector or state subsidized rental housing) attract households with different socio-occupational profiles. In Paris, owners represent the “highest” social structure (most are managers), followed by private-sector tenants, and lastly, tenants of subsidized housing (most of whom are office workers).
7It is quite significant that the author has chosen to study France’s capital city, which differs from other European capitals in that its surface cannot be enlarged. This considerably limits its ability to grow its housing stock, especially since densification options in the city are likewise limited. Faced with spatial pressure and a fall in the average size of households occupying housing units in Paris (explained primarily by population ageing, couple break-up, and the strong attraction Paris holds for small households), the city is now losing more inhabitants every year than it gains. Dittgen shows how, despite a rising number of housing units and the city’s attractive power, which remains strong, the population of Paris has been dropping continuously since the early 1950s.
8One reason the city is so attractive is the high proportion of small rental units – much higher than for the greater Paris metropolitan area. The occupants of these units, single person households or young childless couples, are highly mobile and tend to live in small private-sector apartments, heavily represented in Paris. To this must be added an increasing number of second and occasional homes, the effect of which is to lower the number of units available to Parisians. All these phenomena combined – including a particularly expensive housing stock and a glaring shortage of social or subsidized housing – leads many growing households (couples with a new baby, for example) to leave Paris.
9The second city chosen by the author to illustrate connections between housing characteristics and their potential attractiveness for a given population type is Marne-la-Vallée, one of France’s “new cities.” The new cities were developed between 1975 and 1982 in the Paris area and quickly occupied by a high proportion of young couples who moved there either from Paris or the first ring of suburbs. Here again the author studies the tie between type of housing unit built and the first occupants to arrive. But choosing the new city of Marne-la-Vallée also enables him to study the long-term effects of planned housing construction on school facility needs. This study, an exercise in projection, was based in large part on assumptions about length of occupancy by type of unit: while some units are occupied for a short time only, inhabitants are likely to settle permanently and grow old in others. In the first situation, school facilities will have long-term utility while in the second they will quickly become obsolete. Dittgen’s results show that strong household mobility actually works to stabilize needs and enable cities to get the most out of their facilities, though he also points out that residents can only be mobile if housing supply is varied. He concludes by explaining the perverse effects of having a uniform housing stock of the sort found in some French suburbs, with a high proportion of collective low-rent buildings. If housing stock is not mixed, the risk is that a given territory will come to be occupied by a homogeneous, pre-segregated population.
10In the second section, continuous with the first, the author presents and analyses another local projection exercise. Using the examples of Paris and Marne-la-Vallée again, he shows the importance of taking housing into account – i.e., housing unit categories, changes in housing stock, household size but also the size of the population living in single-person households – when making local population projections. Projections of this sort are a complex undertaking, especially because their objectives may be different from those of national population projections. Local projections are more an exercise in simulation, anticipation and assisting local decision-making authorities.
11In population projections, age and sex figures are determined on the basis of assumptions about entry and exit flows (births, deaths and migrations). At the local scale, results are more likely to be reliable if migration movement is low since at this analytical level the main growth factor is mobility. But demographers doing local projections have a fundamental tool for anticipating future migration trends, more effective than methods that merely extrapolate from past trends, and that is: housing. Dittgen stresses the need to take into account local situation diversity in connection with both the structure of the population about which the projection is being made and data on the local real estate market and housing stock trends.
12The third and last section is a set of texts on local demography published in the journal of the Pénombre association. All critically assess how the numbers were arrived at, examining definitions and concepts as well as data collection methods.
13The various studies in this work present the reader with research findings on characteristic French localities. One strong point is that they show all the ways that components of local populations are intertwined and operate jointly, namely through the “housing” variable and residential migration. However, while housing surely plays a crucial role, it is a pity the author did not inquire into other factors that shape territories by inducing local-scale residential migration; i.e., school infrastructure and transport systems, facilities and services and, of course, employment opportunities.