Comptabilité générationnelle et vieillissement démographique : les enseignements d’un modèle d’équilibre général calculable calibré pour la Belgique

In most developed countries, the age distribution of the population is shifting rapidly towards the elderly. If transfers and the tax schedule are unchanged, future generations will then have to bear an increased charge and, consequently, they could be deprived.

This process is the subject of much debate, using tools like the Auerbach et al. (1991, 1993) and Kotlikoff's (1992) generational accounting. These aim to compare the mean charge to be borne by future generations with the net payments of the people presently alive.

In this paper, we first propose an immediate extension of the Auerbach and Kotlikoff's standard generational accounting. We mechanically evaluate the distribution of the inherited charge between the future generations. If we suppose that the income tax is adapted on a yearly basis to meet the instantaneous public budget constraints, for a given debt ratio, people born at the beginning of the next century will be the most charged. These results are presented for the Belgian case.

We then extend the Auerbach and Kotlikoff's standard generational accounting by developing a computable general equilibrium model with overlapping generations in which lifetime is uncertain. The general equilibrium approach yields results that are compatible with the hypothesis of an individual's rational behaviour and with the balancing of the markets. It is shown that the gap occurring between the charges borne by the present generations and the individuals to be born could be much higher than the one estimated through a simple mechanical methodology. This results from a shrinkage of the fiscal basis due to a higher tax on wages.