Diffusion of car ownership and use in France since the mid-70’s

For each quartile of income per consumption unit, annual time-series have been estimated from panel surveys, with annual waves of observations since 1974: - INSEE Households' Continuous survey from 1974 to 1994, - Sofres 'Parc-Auto' panel survey since 1994. In these data sources, household behaviour is described through: - car ownership (percentages of households with at least one car, and of multi-car households,average number of cars per adult over 18, which is the minimum age for obtaining a driving license in France), - car use (annual mileage per household or per car). The repeated sample structure of data has been used for improving the accuracy of time-series of variables highly correlated for successive years. In mid-70's, car ownership and use were quite low for the poorest income quartile, but the gap has much decreased with the three higher income groups, which have a more homogeneous behaviour. Thus, multi-car ownership, which is mainly structured by geographic and demographic determinants, has slowed -but not reversed- the social diffusion of automobile. After a period of stability between the mid-80's and the early 90's, the social diffusion of automobile has started again like in the 70's, especially for low-income groups and in low-density areas where no alternative to car use is available. However, the Q4/Q1 index has almost stabilised in the 2000's, at national level as well as in Paris region, showing that this diffusion seems to reach its limits. As the curves representing car ownership (number of cars per adult) and car use (annual mileage per household) seem to become quite horizontal during the most recent period, logistic curves have been estimated for each quartile of the distribution of households by income per consumption unit, according to time, then to real income. Saturation thresholds are estimated, as well as the date of the point of inflection. The relationship between temporal elasticities (for each quartile) and crosssectional income elasticities, which could be considered as a measurement of inequality at each point in time, will be discussed (Gardes and Madre, 2005)