Explaining Customer Loyalty in Port Services: Evidence from an Emerging Port System Using PLS-SEM and Necessary Condition Analysis

This study investigates customer loyalty in port services by integrating sufficiency and necessity perspectives within a customer evaluation framework incorporating port service performance and green port initiatives. Using survey data collected from 368 port users in an emerging port system, the study employs Partial Least Squares Structural Equation Modeling (PLS-SEM) and Necessary Condition Analysis (NCA) to distinguish between factors that enhance customer loyalty and conditions that are indispensable for loyalty to occur. The results indicate that green port initiatives primarily influence customer evaluations through port image rather than directly affecting customer satisfaction or loyalty. Environmental awareness significantly strengthens the relationship between green port initiatives and port image, while sequential mediation analysis confirms that both green port initiatives and port service performance influence customer loyalty through the combined pathway of port image and customer satisfaction. Importantly, customer satisfaction emerged as both the strongest predictor and the strongest necessary condition for achieving high levels of customer loyalty, whereas port image and port service performance exhibited comparatively weaker necessity effects. These findings reveal the existence of non-compensatory threshold effects that cannot be captured by conventional sufficiency-based approaches alone. The study contributes to customer loyalty research by demonstrating that customer satisfaction functions not only as a mediating mechanism but also as a gatekeeping mechanism governing whether high levels of customer loyalty can be achieved. Methodologically, the complementary use of PLS-SEM and NCA distinguishes factors that enhance customer loyalty from conditions that are necessary for its occurrence. The study further contributes empirical evidence from an emerging port system, demonstrating that influential drivers are not necessarily indispensable conditions for customer loyalty.