Multi-objective programming model for determining the efficiency and returns to scale in supply chain management of two-stage: a case study of resin companies in Iran

In recent years, a new approach which has been dominant over operation management is the “supply chain management approach”. Supply chain management has attracted most researcher's attentions in recent years. This is the way to improve the economic, social and environmental performance. Therefore, the evaluation of SSCM is an important task for all types of organizations. Among the methods of evaluation SSCM, it seems that data envelopment analysis (DEA) is an appropriate approach. Some of decision-making units composed of several sections or stages that make a network of sub-processes. In order to evaluate such units, data envelopment analysis (DEA) is applied. This paper presents two approaches to calculate supply chain management as a network process. In the first approach, we consider the generalization of weighted sum model to calculate efficiency and returns to scale (RTS) of supply chain with two-stage process as single-objective approach. In the second one, we introduce the weighted sum model to calculate efficiency and returns to scale (RTS) of supply chain with two-stage process as multi-minded approach, so we try to make it to be single-objective approach and then calculate the efficiency of its total production process, according to the decision-maker's ideas and interests. In the next section of this paper according to the two above approaches, we determine the percent of returns to scale (RTS) of supply chain. Suggested ideas are used to evaluate the efficiency and returns to scale (RTS) of supply chain in resin production companies.