efficiency measurement in two-stage network structures considering undesirable outputs

since data envelopment analysis (dea) introduced in 1970s, it has been widely applied to measure the efficiency of a wide variety of production and operation systems. recently dea has been extended to examine the efficiency of decision making units (dmus) with two-stage network structures or processes, where the outputs from the first stage are intermediate measures that make up the inputs of the second stage. many researchers developed several dea based models for evaluating the efficiencies of such systems. this paper considers evaluation of the general two-stage network structures, while each stage may produce undesirable output, in addition to desirable ones. the developed model is applied to green hen poultry chain in guilan province, iran.