a model for efficiency evaluation in basic two-stage dea network systems with different proportionality

Several models have been proposed for efficiency evaluations in product theory in the frameworks of both conventional and network data envelopment analysis (dea). these models, in terms of returns to scale (rts), examine the range from full proportionality to disproportionality and often assume the systems under consideration to prevail only with a single rts. plenty of efforts have been made in conventional dea to allow variable proportionality, the outcome of which has been reflected in the remarkable work of podinovski (2004). in this paper, we have incorporated variable proportionality with basic two-stage network dea to evaluate efficiencies of decision making units (dmus). here, we assume that each dmu consists of two divisions that work in series so that the first division exhibits constant rts (crs) and the second one exhibits variable rts (vrs).