Gollier, C., van der Ploeg, F. and Zheng, J. (2023). The discounting premium puzzle: Survey evidence from professional economists Journal of Environmental Economics and Management, 122:.

We surveyed economists{\textquoteright} attitudes toward adjusting discount rates to the risk profile of public programs. Three-quarters of respondents recommend to use project-specific discount rates. For example, on average, respondents discount railway infrastructures more than hospitals and climate mitigation. But the degree of discount discrimination between distinct risk profiles of different projects is fairly limited in our sample given the differences in risk profiles for these projects. Economic experts thus penalize risky public projects far less than financial markets penalize private investments. We call this the ”discount premium puzzle”. Finally, among experts in favor of a single discount rate, there is no consensus on whether it should be based on the average cost of capital in the economy, the sovereign borrowing cost, or the Ramsey rule, which gives rise to disagreement over the level of the recommended discount rate.