Slacks based measure or SBM analsysis is a non-radial model to solve the problem in the “additive model” developed by Charnes, Cooper, & Rhodes in 1978. This model can discriminate between efficient and inefficient Decision-Making Units (DMU).
Variable returns to scale (VRS) is a type of frontier scale used in data envelopment analysis (DEA). It helps to estimate efficiencies whether an increase or decrease in input or outputs does not result in a proportional change in the outputs or inputs respectively (Cooper, Seiford, & Zhu, 2011).
The previous article depicts the analysis and interpretation of the Input oriented multi-staged constant returns to scale (CRS). Output oriented multi-staged Constant returns to scale data envelopment analysis (CRS-DEA) is, however, based on a different principle.