Measurement of Dynamic Efficiency: A Relational DEA Model

In Data Envelopment Analysis (DEA) literature, dynamic DEA models are used to measure the efficiency of systems involving changes in inputs and outputs over time. In this paper we propose a relational dynamic DEA model, by considering the intermediate products among periods within the system. Under this framework, the overall efficiency of the system is expressed as a weighted sum of the efficiencies of its periods. Using this model we can measure the dynamic efficiency of the whole periods as well as the efficiency of each of the periods. This helps the decision maker recognizes inefficient periods and make later improvements. A numerical example of gas companies in Iran from literature is used to clarify the model