Against High Discount Rates

Abstract

In the economics of climate change, the future benefits of greenhouse gas emissions abatement are commonly discounted at a rate equal to the long-run return on corporate stocks, which averaged 6% per year during the 20 th century. Since a 6% discount rate implies that one dollar of benefits obtained one century from the present attains a present value of less than one cent, this method implies that only modest steps towards greenhouse gas emissions are economically warranted. This chapter critiques this approach to discounting the future based on three distinct lines of reasoning. First, the use of high discount rates is inconsistent with classical utilitarianism, which holds that equal weight should be attached to the welfare of present and future generations. Second, the approach violates the principle of stewardship, which holds that it is morally unjust for present generations to engage in actions that impose uncompensated environmental costs on posterity. Third, the use of a 6% discount rate is appropriate in the analysis of public policies that have risk characteristics that are similar to those associated with corporate stocks. Economic theory, however, suggests that discount rates of 1% or less should be used to evaluate policies that reduce future risks. Since a main objective of climate change policies is to reduce the risks faced by future society, the use of high discount rates in the analysis of climate change policies is arguably inappropriate.

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