network ‎d‎ata envelopment analysis models for measuring efficiency of a four-stage supply chain with returned outputs‎

In this paper, while data envelopment analysis (dea) technique has been used, four-stage dea model mooted in order to consider the situation in which there exist returned products. these products are neither nal products nor inputs of the next sub-process. these returned products are the inputs of previous sub-processes that need to be processed again due to existence of aws. here a supply chain with four stages as supplier, manufacture, distributor and retailer with intermediate and return products has been considered and a dea model formulated for analyzing it. also, with an application validity of the proposed model has been demonstrated.