Origination of a Sustainable Manufacturing Index for Evaluating the Environmental and Social Performance of Small and Medium Enterprises in Nigerian Industrial Clusters

Existing sustainability performance measurement frameworks for manufacturing enterprises were developed within the institutional, regulatory, and reporting contexts of industrialised economies and apply inadequately to the informal and semi-formal organisational structures, data scarcity conditions, and context-specific social dimensions of manufacturing enterprises in Nigerian industrial clusters, necessitating the origination of a contextually appropriate and theoretically defensible assessment instrument. This research originates a Sustainable Manufacturing Index specifically designed for small and medium-scale manufacturing enterprises in Nigerian industrial clusters, developed through a mixed-methods research programme spanning the Aba, Nnewi, Kano, and Kaduna manufacturing clusters representing South East, North West, and North Central geopolitical zones. The index construction methodology integrates a novel theoretical framework for sustainable manufacturing assessment in informal economy contexts, drawing on stakeholder theory, institutional theory, and the capabilities approach to reframe sustainability dimensions appropriate to the Nigerian SME context. Delphi method consensus-building with 44 expert panellists from industry, academia, and regulatory bodies across three rounds establishes the domain structure, indicators, and relative weightings of the index. Structural equation modelling using partial least squares is applied to data from 210 enterprises to validate the measurement model's convergent validity, discriminant validity, and predictive reliability. The validated index discriminates meaningfully between sustainability performance tiers across the enterprise sample and exhibits test-retest reliability of 0.87. The research constitutes an original methodological contribution to sustainable manufacturing assessment theory in developing economy contexts. Keywords: sustainable manufacturing index, SME, Nigerian industrial clusters, sustainability assessment, informal economy.