An Assessment of the Widespread Use of Increasing Block Tariffs in the Municipal Water Supply Sector

The design of municipal water tariffs requires balancing multiple criteria such as financial self-sufficiency for the service provider, equity among customers, and economic efficiency for society. Globally, various forms of water tariffs are in use (e.g., tariffs based on fixed or volumetric charges, single and two-part tariffs, and increasing or decreasing block tariffs) but increasing block tariffs (IBTs) have become popular worldwide over the last few decades for two main reasons. Apart from the fact that IBTs incentivize households to save water by charging large volumes at a higher price, there is a widespread belief that IBTs are pro-poor. The latter would be the consequence of providing all households with a minimum amount of water at a low (subsidized) price while large water users pay higher prices. However cross-subsidization between wealthy and poor households will occur only if poor households’ consumption falls in the low (subsidized) block and if rich households consume in the higher block and pay a price that is above the average cost of supply. These two conditions are rarely met in reality and IBTs often fail to allocate subsidies to the poor effectively. There are a few examples of water utilities making adjustments to the tariff to take into account that poor households with large families are likely to be adversely affected by IBTs. However, the provision of a minimum amount of water for free (as in South Africa), the design of household-specific low-cost water allowances (as in California), or tariffs being adjusted based on household size do not usually improve the targeting of subsidies to the poorest households. The widespread use of IBTs is difficult to rationalize, in particular while knowing that the use of a (simple) uniform volumetric tariff where water provision is charged at its full cost could improve social welfare by removing price distortions and would be easier for households to understand than IBTs. This simple tariff could be combined with some consumer assistance programs to help the poorest households pay their bills.

Multiple Goals Dilemma of Residential Water Pricing Policy Reform: Increasing Block Tariffs or a Uniform Tariff with Rebate?

Water is a basic necessity and its allocation and utilization, especially pricing policies, impose various social, economic, and ecological impacts on social groups. Increasing block tariffs (IBTs) has gained popularity because it is expected to incentivize water conservation while protecting poor people benefiting from the redistribution effects because of its nonlinear tariff structure. However, it results in price distortion under certain circumstances. Researchers have also proposed an alternative practical price system and a uniform tariff with rebate (UTR), with the price level set equal to the marginal social cost and a fixed rebate allocated to the poor groups. This study proceeds with a simulation of the two pricing systems, UTR and IBTs, and empirically explores their fundamental merits and limitations. The results confirm the theoretical perspective that a water price system, compared with an optimal tariff system, simultaneously achieves multiple goals to the greatest possible extent.

Increasing Block Tariffs in the Water Sector – An Interpretation in Terms of Social Preferences

Many developing countries around the world apply progressive water tariffs, often structured in the form of discretely increasing block tariffs (IBTs). These tariffs have been criticized in the welfare economic literature due to their perceived inefficiency: many of the prices charged under IBTs do not correspond to marginal costs and thus violate the principle of allocative efficiency. In this paper we explore an alternative interpretation of the widespread use of IBTs, in terms of social preferences and fairness considerations. For this, we rely on an extension of the Fehr, E., and K. Schmidt (1999. “A Theory of Fairness, Competition, and Cooperation.”Quarterly Journal of Economics114: 817–868.) utility function, including inequality aversion, to which we add another parameter representing a reference for redistribution which reflects a societal preference to correct for income difference perceived as unfair. Additionally, the model includes a variable on household size, finding that, as poor households are on average larger, a simple IBT tariff disregarding household size may not be “fair”.