Cross-Disciplinary Evidence for Hyperbolic Social Discount Rates
不同学科研究发现社会贴现率可能是双曲线而非指数形式；行为研究、部分实证经济学以及英美政府长期项目的贴现实践均支持这一假设，且统计聚合表明即使个人偏好是指数型，群体贴现率仍呈双曲线。
Researchers in different disciplines have independently found evidence to suggest that the social discount rate may be hyperbolic, rather than exponential, in nature. Both behaviorist research and some empirical economics studies support the hyperbolic discounting hypothesis. U.S. and U.K. government discounting dispensations for some long-run public development projects are explicable in terms of an underlying hyperbolic social discount rate. A statistical aggregation argument demonstrates that even if the behaviorist, economics and public choice evidence for hyperbolic discounting is not conclusive, the social discount rate of a set of people who individually express time preferences best modeled by exponential discounting functions is nonetheless hyperbolic. Further empirical economics studies of discounting preferences are required. Comparisons of different national discounting practices would also be useful to see how widespread is the use of unusually low exponential rates of discount for long-run projects. The application of hyperbolic discounting would have most impact in long-run benefit-cost analyses. However, government agencies would require overwhelming evidence before switching from exponential to hyperbolic discounting.