A Composite Quality Index and Multi-Criteria Decision-Support Framework for Evaluating Complaint Resolution Performance of Express Delivery Operators

The rapid expansion of the express delivery sector, driven by the growth of e-commerce, has increased the importance of effective complaint management as an integral component of service quality and consumer protection. Although operational service performance and complaint handling have been widely investigated, existing studies have generally assessed these dimensions separately, leaving a gap in integrated performance evaluation. This study proposes a comprehensive decision-support framework for evaluating complaint resolution performance of express delivery operators by integrating Service Failure Indicators (SFI), Complaint Resolution Indicators (CRI), an Entropy-based Composite Quality Index (CQI), and the MARCOS multi-criteria decision-making method. The proposed framework combines objective operational and complaint-related performance indicators within a unified evaluation model. The CQI is constructed by aggregating three complaint resolution indicators using objectively determined Entropy weights, while the MARCOS method is applied to rank operators according to both operational performance and complaint resolution effectiveness. The applicability of the framework is demonstrated through a case study involving five major express delivery operators in the Republic of Serbia using regulatory operational data. The results reveal meaningful differences in operator performance and show that integrating operational service failures with complaint resolution effectiveness provides a more comprehensive evaluation than evaluating either dimension independently. The proposed framework contributes to the literature by integrating operational service quality evaluation, complaint resolution performance, composite quality measurement, and multi-criteria decision-making into a unified evaluation framework. Furthermore, it provides an objective benchmarking tool that can support regulatory oversight, managerial decision-making, and continuous quality improvement in the express delivery sector.