Propensione aggregata al risparmio, rapporto ricchezza-reddito e distribuzione della ricchezza nel modello del ciclo di vita "egualitario": il ruolo delle variabili demografiche

In this paper we explore the impact of demographic variables on the aggregate propensity to save (PS), on the aggregate wealth income ratio (WIR) and on the distribution of wealth (WD), in the life cycle (LC) "egalitarian" model. We depart from Modigliani and Brumberg (1954) and Atkinson (1971) pioneering papers by assuming that the household, rather than the individual, is the relevant economic unit. More precisely, we allow parents to care about their children, such that consumption (and saving) of the household change when children are born and until the latter join the labor force and form a new household. Under this scenario we show that, in a stationary economy, the timing of births strongly affects both the WIR and the WD, while the dispersion, within each household, of such a timing affects the WD only. In a steadily growing economy due to population growth, the impact of the timing of births and of the number of children turns out to be significant for the PS, the WIR and the WD, in a much stronger manner than in the traditional LC model; moreover, we find that the aggregate propensity to save is a decreasing function of the population growth rate when the latter changes: i) due to the timing of births or ii) due to the number of children and provided that the age of parenthood is sufficiently low. The latter results are in clear contrast with one of the fundamental propositions of the traditional LC theory.