Supplier selection significantly impacts supply chain cost, reliability, and sustainability. This study uses Slack-Based Measure (SBM) Data Envelopment Analysis (DEA) to identify and evaluate supplier congestion in a cosmetic supply chain, which negatively impacts cost, reliability, and sustainability. The SBM-DEA model assesses suppliers based on input excesses and output shortfalls, distinguishing between efficient, inefficient, and congested suppliers—a state where increased inputs lead to decreased outputs. A case study evaluating 10 suppliers across 9 criteria identified resource congestion in one supplier due to overutilization. Of the suppliers studied, 4 were efficient, and 6 were inefficient. This framework offers practical insights for optimizing supplier selection and resource allocation to improve supply chain efficiency, reduce costs, and enhance performance. The findings underscore the importance of congestion analysis in supplier evaluation, enabling data-driven decision-making and providing theoretical and practical contributions to supply chain management by helping procurement managers address supplier inefficiencies.
