L'impact du vieillissement démographique sur les mécanismes macroéconomiques

The first aim of this report is to present a synthesis of the analysis of pension schemes. We neglect any individual heterogeneity and focus on intertemporal trade-offs. The Diamond model shows that a pay-as- you-go pension scheme exerts a negative effect on saving and capital accumulation Moreover, it is likely that the rate of return of a fully-funded system will be higher than the one of a pay-as-you-go system. The necessity to provide for the pensions of the current old generation does not allow us to infer the optimality of the fullyfunded system however. An intertemporal approach demonstrates that the optimal system depends very much on the social rate of discount. Moreover, this approach also demonstrates a neutrality property of public debt. An instantaneous switch to a fully-funded scheme, supported by public debt in order to provide for initial pensions, is shown to be equivalent to a gradual phasing-out of a pay-as-you-go system. Sections on altruism and risk complete this synthesis. The second part of the paper is devoted to an analysis of the consequences of ageing. The standard two-period overlapping-generation model is of no help as its sole demographic parameter is the birth rate. We therefore modify this model to distinguish the effects of individual ageing from changes in the birth rate. To this end, we simply assume that the agents do not live out their entire second period of life. We also focus on a mixed pension scheme that is fully funded, but offers agents an actuarially fair choice on their retirement age. Numerical simulations describe possible responses to the dilemmas France currently faces. A deferring of the retirement age appear an unavoidable element.