Sommes-nous trop égoïstes ou trop généreux envers les générations futures ?

In our Western economies, the abnegation of past generations has contributed to improving current generations? welfare. What about now? Under the pressure of ecological catastrophists, is the current generation too burdened in favor of future generations or on the contrary, is it not burdened enough in view of the risks to be borne by our descendants? In this paper, I review the importance, for public decision making, of the choice of discount rate used to assess the present value of the flow of future damages (or benefits) linked to the current decisions. I then develop a classical model identifying the efficient social discount rate and analyze its determinants (pure rate of time preference, wealth effect and precautionary effect). Relying on empirical evidence and the historical trend of the economic growth rate, I discuss what is a reasonable value for the discount rate according to the term of the assessed project.