A life-expectancy-Period-Cohort model to project private car fleet and traffic applied to France

Résumé Fr

in most industrial countries, after decades of gradually slowed growth, car traffic stagnated in the 2000s. This phenomenon has been attributed not only to conventional economic factors (stagnation of incomes, upward volatility in fuel prices) and to re-urbanization linked to metropolisation, but also to demographic factors (ageing of the population, longer life cycle stages leading in particular to delay the passage of the driving license in the younger generations). The economic recovery, albeit rather slow, and a signification drop in the price of oil in 2014 favored a certain revival of traffic growth in several countries (USA, Germany, France,...); but what about the structural factors and how to predict medium-term developments ? We have already dealt with these questions via Age-Period-Cohort models, and more often Age-Cohort (AC). In view of the over-determination generated by the mechanical link between these three factors, we propose a Life-Expectancy-Period-Cohort model (EPC); indeed, by replacing age by life expectancy at this age and at each date, the model can be directly estimated keeping the three components, while making this approach more consistent with the extension of life cycle stages (longer studies, women having thei children in their thirties, postponement of retirement age, ...). Period effects are specified by introducing the income of the household and a fuel price index as explanatory variables. The results are compared with those of various previous models.