Policymakers and utility managers can use a variety of tariff structures to calculate customers' bills for water and sanitation services, ranging from a simple fixed monthly fee to complicated multi-part tariffs with seasonal pricing based on metered water use. This study examines the performance of several alternative tariff structures for water and wastewater services in Nairobi, Kenya using a dynamic tariff simulation model applied to a complete set of billing records from Nairobi City Water and Sewer Company. Simulations show that a uniform volumetric price tariff structure performs as well as or better than several increasing block tariff (IBT) structures across the six performance metrics considered (customer welfare, social welfare, cost recovery, the subsidy delivered through the tariff, subsidy incidence, and water conservation). These findings are robust to changes in the level of cost recovery. This finding challenges the wisdom of the widespread use of IBTs in low- and middle-income countries and current perceptions of best practice in tariff design.

中文翻译：

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评估水和卫生关税的表现：肯尼亚内罗毕的案例

政策制定者和公用事业经理可以使用各种关税结构来计算客户的水和卫生服务账单，从简单的固定月费到复杂的多部分关税，以及基于计量用水的季节性定价。本研究使用适用于内罗毕市供水和下水道公司的完整计费记录集的动态关税模拟模型，检查肯尼亚内罗毕供水和污水处理服务的几种替代关税结构的性能。模拟表明，在所考虑的六个绩效指标（客户福利、社会福利、成本回收、通过关税提供的补贴、补贴发生率、和节水）。这些发现对于成本回收水平的变化是稳健的。这一发现挑战了中低收入国家广泛使用 IBT 的智慧，以及目前对关税设计最佳实践的看法。