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Abstracts
Résumé
En faisons-nous assez pour les générations futures? Cette question est sous-jacente à de nombreuses questions économiques actuelles, comme celles de la réduction de la dette, de la réforme des retraites, de la lutte contre le changement climatique, de la préservation des ressources naturelles, des investissements d’infrastructure ou de la fiscalité de l’épargne par exemple. Notre responsabilité sociale envers les générations futures se traduit en termes économiques par le taux d’actualisation, qui donne une valeur au futur relativement au présent, et qui détermine l’arbitrage présent/futur des agents économiques. Si on reconnaît qu’une société court-termiste utilise un taux d’actualisation trop élevé, comment déterminer le niveau désirable de ce taux? Dans cet article, je synthétise les importants développements scientifiques récents sur ce sujet. Étant donné la baisse tendancielle de nos anticipations de croissance et les fortes incertitudes sur les évolutions longues de notre société, je recommande un taux sans risque de deux fois le taux de croissance anticipé de la consommation (pour actualiser des cash flows engendrés sur les horizons inférieurs à 20 ans) à 1 % (pour des maturités au-delà de 100 ans). La prime de risque devrait aussi avoir une structure par terme, s’étalant de 1 % à court terme jusqu’à 3 % pour le long terme.
Abstract
Do we do enough for the future? This question is related to many different current issues, from the reduction of sovereign debt in Europe, to the pension reform, the fight against climate change, the preservation of natural resources, the level of public investment in infrastructure, or the fiscal treatment of long-term savings for example. Our social responsibility towards future generations is decentralized through the choice of the discount rate, which determines the tradeoff between present sacrifices and future benefits. How should we define the efficient level of long-termism? In this paper, I summarize the most important evolutions in the economic analysis of this question in recent years. Given the strong uncertainties that prevail concerning the long term evolution of our society, I recommend to use a discount rate ranging from 2 times the anticipated growth rate of consumption for short time horizons, going down to 1 % for time horizons above 100 years. The systematic risk premium should also have a term structure, starting at around 1 % for short maturities to 3 % for extra-long ones.
Appendices
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