Analysis of Persistence and Long-term Trends of Efficiency in Iran's Oil Refineries using a Window Analysis Method

This study, by using data envelopment window analysis method examines the efficiency of 9 Iran’s oil refinery over the period of 2008-2013. Results of the study has shown that, during the period of study, only Kermanshah refinery was efficient in four windows and the rest of the refineries have experienced a stable trend of inefficiency. The inefficiency of oil refining companies has been mostly due to inefficiency in resource management. Inefficient companies in the field of scale efficiency have had a decreasing return to scale, that can be achieved by reducing the size of the company to the optimal scale. The highest amount of resources wasted in the refineries was related to the refinery's fuel and feed consumption. Isfahan refinery had the highest loss of capacity, fuel and feed consumption, and Abadan refinery had the most labor force wastage.