Sustainable supplier selection model with a trade-off between supplier development and supplier switching

Due to growing concerns regarding sustainability, purchasing decisions are challenging and difficult tasks for decision-makers. This difficulty has compelled purchasing companies to know and understand the whole purchasing process and to give importance to purchasing associated decisions. A long-term relationship and investment are required for purchasing decisions because they impact significantly on a company’s performance and supply chain. Hence, supplier selection and sourcing strategy selection decisions are among a firm’s most important problems. In this study, sourcing strategy decisions include supplier development, which helps suppliers to improve their performance, and supplier switching, which searches for more proficient alternatives for supply. To solve these problems, this study provides an integrated multi-criteria decision-making (MCDM) model. The model contains four stages. First, the right set of sustainable key performance indicators (SKPIs) for evaluating the performance of suppliers is identified through a literature survey and discussions with the decision-making team. Second, the best worst method-measurement of alternatives and ranking according to the compromise solution method (BWM-MARCOS) approach is applied to determine the priority weights of SKPIs and the priority weights of incumbent and new suppliers based on identified SKPIs. Third, a bi-objective mathematical model is developed to determine which optimum sourcing strategy and potential supplier should be chosen based on the priority of incumbent and new suppliers while optimizing cost and sustainable performance. Fourth, the mathematical model is solved using Epsilon constraint method and min–max fuzzy approach. The applicability and efficiency of the proposed integrated MCDM model is demonstrated with a real case study from a home appliance manufacturing company. The key findings reveal that the proposed model can be utilized for strategic and effective sourcing planning. One of the important contributions of this work is to provide suggestions for deciding the appropriate sourcing strategy for suppliers using the outputs of the mathematical model.