自从1990年夏天，作为自愿保护计划的一部分，水电部启动了家庭水资源调查计划以来，洛杉矶市已经进行了两万多次居民水资源调查。市场营销信函被发送到排名前20%的用水家庭账户，并完成了大约5000项调查。在接下来的一年里，强制实施的保护目标导致对第二次家庭用水审计的响应大幅增加。1993年的第三次营销活动与一种新的费率结构同时进行，该结构对更高水平的用水征收更高的价格。因为家庭调查的设计——包括安装厕所排水装置、改装旧淋浴头和水龙头曝气器、泄漏检测和维修，以及执行室外灌溉效率审计- -在项目的三个阶段保持不变，这些数据代表了一个近乎理想的自然实验。家庭用水需求的统计模型用于将家庭用水特征、气候措施和水价数据的检查数据与计量用水的变化联系起来。这些经验模型给出了具体的答案，既说明了节约了多少水，也说明了为什么项目不同阶段的节约水平可能不同；特定阶段内的不同家庭；一年中不同的季节；以及不同的时间长度（即储蓄的持续性）。这项研究的方法和结果应该引起保护协调员和水资源规划人员的兴趣，他们需要知道这种需求的可靠回报- 附带投资。

The City of Los Angeles has performed over twenty thousand residential water surveys since the Department of Water and Power initiated its Home Water Survey Program in the summer of 1990 as part of its voluntary conservation program. Marketing letters were sent out to single family accounts that ranked at the top 20 percent of water use and approximately five thousand surveys were completed. In the following year, the imposition of mandatory conservation targets resulted in a vastly increased response to a second offer of home water audits. A third marketing effort in 1993 was timed in conjunction with a new rate structure that imposed a higher price for higher levels of water use. Because of the design of the home survey--consisting of installation of toilet displacement devices, retrofit of old showerheads and faucet aerators, leak detection and repair, and performance of an outdoor irrigation efficiency audit--remained constant through the three phases of the program, these data represent a nearly ideal natural experiment. Statistical models of household water demand are used to link the inspection data on household water-using characteristics, climatic measures, and water rate data with changes in metered water use. These empirical models yield concrete answers to both how much water was saved and why the level of conservation may be different for the different phases of the program; different households within a given phase; different seasons of the year; and different lengths of time (i.e. the persistence of savings). The method and results of this study should interest conservation coordinators and water resource planners who need to know the reliable payoff from this type of demand-side investment.