Data from: The low but uncertain measured benefits of U.S. water quality policy

US investment to decrease pollution in rivers, lakes, and other surface
waters has exceeded $1.9 trillion since 1960, and has also exceeded the
cost of most other US environmental initiatives. These investments come
both from the 1972 Clean Water Act and the largely voluntary efforts to
control pollution from agriculture and urban runoff. This paper reviews
the methods and conclusions of about 20 recent evaluations of these
policies. Surprisingly, most analyses estimate that these policies’
benefits are much smaller than their costs; the benefit/cost ratio from
the median study is 0.37. However, existing evidence is limited and
undercounts many types of benefits. We conclude that it is unclear whether
many of these regulations truly fail a benefit/cost test or whether
existing evidence understates their net benefits; we also describe
specific questions that when answered would help eliminate this
uncertainty.

自1960年以来，美国在河流、湖泊及其他地表水域污染治理方面的投资累计已超1.9万亿美元，且其规模远超美国绝大多数其他环境倡议的投入成本。此类投资资金来源既有1972年《清洁水法案》（Clean Water Act）的规制要求，也涵盖了农业与城市径流污染治理领域的大量自愿性行动。本文综述了针对上述政策的约20项近期评估研究的方法与核心结论。出乎意料的是，绝大多数分析结果显示，这些政策的收益远低于其投入成本；所有中位研究的收益成本比仅为0.37。但现有研究证据存在局限性，且未充分统计诸多类型的政策收益。本研究认为，目前尚无法明确：究竟是这些监管政策本身未通过收益成本检验，还是现有研究低估了其净收益。同时，本文还阐述了若干具体研究问题，厘清这些问题将有助于消除当前的研究不确定性。