Demographic change and transformations of the active life cycle: what relations?#(in French)
Historical changes in the typical life-cycle do not conform to a simple model of equal-sharing in which additional years of life are equally distributed between time devoted to training, work and leisure. We have instead observed a quasi-general decline in the share of our life-cycles that is devoted to labour. The major reason for such a deviation is the fact that this life-cycle evolves in response to other factors, such as productivity, preferences and conditions for the accumulation and depreciation of human capital. We investigate the articulation of these different factors in a continuous-time model of life-cycle optimisation that allows a realistic treatment of demographic structure. The main motives for the contraction of working lives are global productivity and the importance of human capital depreciation. We show that the equal-sharing scenario requires a parallel evolution of productivity and consumption norms, and a slowing-down of human capital depreciation that is consistent with the change in life expectancy.