Alternative household water affordability metrics using water bill delinquency behavior

Abstract

Rising water prices threaten affordable access to basic water service in the U.S., especially in low-income communities. Faced with unaffordable water bills, households may use less water than is healthy, forgo other essential services, or fall behind on water bill payments, risking water shutoffs. Affordability ratios (ARs), which express water bills as a fraction of income, are the most common measure of water affordability. However, ARs can underestimate unaffordability due to both spatial aggregation bias and their reliance on indirect proxies for ability to pay. New metrics are needed to identify households at risk of water insecurity due to affordability challenges. Here we investigate alternative water affordability metrics that use water bill late payments and debt to track actual payment behavior at the household level. We define metrics that capture the frequency, duration, and severity of water bill delinquency. We apply these metrics to a case study in Santa Cruz, California, using monthly billing data for approximately 40 000 households from 2009 through 2021. We find large variation in delinquency across households and over time, with higher delinquency linked to proxies for low wealth such as lower assessed home value. Census blocks with similar ARs often have distinct patterns of delinquency behavior, suggesting that block-level median affordability estimates may be masking sub-populations facing affordability challenges. These results highlight the benefits of using multiple, household-level metrics to capture the role affordability plays in household water security.