Traditional studies in two-stage data envelopment analysis (DEA) assumed that the outputs of the first stage completely input into the second stage. But we think that assumption is not realistic becauses of efficiency loss. This paper modifies the traditional relational two-stage DEA with Variable Returns to Scale (VRS) by abandon this assumption. By introduction of efficiency loss to measure t...

It is customary to analyze transport industry structure using two indices: economies of density and economies of scale with variable network size (RTS). The latter has been defined to analyze the behavior of costs when output and network size expand simultaneously. After reviewing in detail what is intended with the calculation of RTS under this definition, we show analytically that, when the s...