| Costs and benefits in the distant future-such as those associated with global warming, long-lived infrastructure, hazardous and radioactive waste, and biodiversity-often have little value today when measured with conventional discount rates. We demonstrate that when the future path of this conventional rate is uncertain and persistent (i.e., highly correlated over time), the distant future should be discounted at lower rates than suggested by the current rate. We then use two centuries of data on U.S. interest rates to quantify this effect. Using both random walk and mean-reverting models, we compute the certainty-equivalent rate that is, the single discount rate that summarizes the effect of uncertainty and measures the appropriate forward rate of... |
