An Integrated Trend Analysis and Grey Relational Analysis of the Macroeconomic and Environmental Determinants of Sustainable Sanitation Infrastructure in Türkiye

Abstract

Sustainable sanitation infrastructure, a critical component of the Water, Sanitation, and Hygiene (WASH) nexus, possesses a multidimensional structure shaped by the complex interactions of macroeconomic and environmental dynamics, including economic growth, rapid urbanization, increasing energy demand, and the filtration capacity of natural ecosystems. High multicollinearity and limited sample sizes in environmental time series often compromise the reliability of traditional regression models. While existing studies in the literature are generally limited to single rankings, this research aims to fill a methodological gap by integrating ranking reliability with dynamic temporal changes. In this study, the socioeconomic and environmental factors associated with safely managed sanitation services, used as a proxy indicator for water and environmental infrastructure sustainability in Türkiye, were examined. Grey Relational Analysis (GRA), which is robust against multicollinearity and effective for small samples, was utilized to determine the relative importance of the variables. The statistical stability of the obtained ranking was tested using the Moving Block Bootstrap resampling method, while temporal trends were analyzed via the Mann-Kendall trend test and Sen’s slope estimator. GRA and Bootstrap results indicated that forest area (representing the natural filtration and assimilation capacity of basins) and GDP per capita have the highest and most statistically stable relational levels with sanitation sustainability. Trend analyses indicated significant increasing trends in sanitation infrastructure, economic growth, energy use, and urban population, whereas a statistically significant decreasing trend was detected in the proportional share of renewable energy consumption within total energy demand. The findings indicate that sustainable infrastructure policies must simultaneously incorporate environmental strategies that enhance natural assimilation capacity, such as forest conservation, alongside economic investments. By validating classical GRA results with Bootstrap and integrating them with temporal trends, this study offers a reliable, holistic, and reproducible analytical framework for policymakers in the WASH infrastructure and environmental engineering literature.

Keywords

• Sustainable sanitation infrastructure
• Grey Relational Analysis
• Bootstrap resampling
• Mann-Kendall trend test
• Sen’s slope estimator

Ethical Statement

Ethics committee approval was not required for this study because no human participants or animals were involved.

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