Non-marginal cost-benefit analysis and the tyranny of discounting

This paper uses the Kaldor-Hicks compensation principle to compute the present value (PV) of a non-marginal future event. Three theoretical results stand out: First, decreasing returns to capital create a wedge between the PV of future generations' willingness to pay (WTP) and the PV of their willingness to accept compensation (WTA); second, the discount rates implicit in the computation of the PVs are endogenous, and rising (declining) over time for the future generations' WTP (WTA); and third, decreasing returns to capital may make it impossible to compensate future generations according to their WTA, effectively defeating the tyranny of discounting. A back-of-the-envelope calibration suggests that this last result is realistic in the case of climate change. A cost-benefit analysis based on the Kaldor-Hicks compensation principle may therefore be impossible if future generations are entitled to a world without climate change; and an environmental trust fund - no matter how large it is - may be insufficient to adequately compensate future generations.