Studies in both corporate fi nance and environmental economics have described how discount rates should vary with the maturity of a project. The former suggests that the cost of capital should increase with the time horizon of the cash flow, while the latter recommends declining term structures...

As the most important driver of long-term project evaluation, from climate change policy to infrastructure investments, the social discount rate (SDR) has been subject to heated debate among economists. To uncover the extent and sources of disagreement, we report the results of a survey of over...