Cutler David, Miller Grant
Department of Economics, Harvard University and National Bureau of Economic Research (NBER), 1875 Cambridge Street, Cambridge, MA 02138, USA.
Demography. 2005 Feb;42(1):1-22. doi: 10.1353/dem.2005.0002.
Mortality rates in the United States fell more rapidly during the late nineteenth and early twentieth centuries than in any other period in American history. This decline coincided with an epidemiological transition and the disappearance of a mortality "penalty" associated with living in urban areas. There is little empirical evidence and much unresolved debate about what caused these improvements, however. In this article, we report the causal influence of clean water technologies--filtration and chlorination--on mortality in major cities during the early twentieth century. Plausibly exogenous variation in the timing and location of technology adoption was used to identify these effects, and the validity of this identifying assumption is examined in detail. We found that clean water was responsible for nearly half the total mortality reduction in major cities, three quarters of the infant mortality reduction, and nearly two thirds of the child mortality reduction. Rough calculations suggest that the social rate of return to these technologies was greater than 23 to 1, with a cost per person-year saved by clean water of about dollar 500 in 2003 dollars. Implications for developing countries are briefly considered.
19世纪末20世纪初，美国的死亡率下降速度比美国历史上的任何其他时期都要快。这种下降与流行病学转变以及与城市生活相关的死亡率“惩罚”的消失同时发生。然而，关于是什么导致了这些改善，几乎没有实证证据，且存在许多未解决的争论。在本文中，我们报告了清洁水技术——过滤和氯化——对20世纪初主要城市死亡率的因果影响。采用技术的时间和地点的合理外生变化来识别这些影响，并详细检验了这一识别假设的有效性。我们发现，清洁水导致主要城市总死亡率降低近一半，婴儿死亡率降低四分之三，儿童死亡率降低近三分之二。粗略计算表明，这些技术的社会回报率大于23比1，以2003年美元计算，清洁水每人每年节省的成本约为500美元。本文简要考虑了对发展中国家的影响。
