Water Poverty Traps: Modeling Heterogeneous Effects of Public Investment and Household Water Expenditure in Different Natural Regions and Poverty Strata in Peru (Cohort 2017 and 2023)

Currently, access to safe drinking water in developing countries remains a structural challenge. Despite progress, many households still lack access to clean and safe water, leading to serious consequences for health, human dignity, and the economy. This research aims to evaluate the impact of drinking water and sanitation investment projects on monetary expenditures for water consumption. Using data from the 2017 and 2023 National Household Survey (ENAHO-INEI) in Peru, a longitudinal study with a retrospective cohort design was conducted. The complex, probabilistic sampling method allowed for modeling both periods using ordered multiple response logit regression. The results show that household connections to potable water positively impacted water consumption expenditures in 2017 (n = 21,251) and 2023 (n = 19,482). Similarly, connections to sanitation facilities positively influenced expenditures in 2017, although no significant evidence was found in 2023. Having access to safe water (adequate chlorine) versus unsafe water (inadequate chlorine) showed a positive effect on consumption expenditures in both years, reflecting that families must bear a double expense to access alternatives such as bottled water. A higher monthly income of the head of household, associated with greater age and years of education, increases expenditures on potable water, excluding households in monetary poverty. A differentiated design of water policies is recommended, based on natural region (coast, highlands, and rainforest) and area (urban or rural), considering the different water access alternatives according to the geographic location of the dwelling.