group ranking of bank units according to data envelopment analysis approach

efficiency calculations for units belonging to one group according to data envelopment analysis widely have received attention; while experiences related to efficiency comparison of several groups consisted of decision making units is restricted. kao's parallel system network dea model that has been designated aimed at such a comparison, practically leads to accomplish comparison among units instead of groups. this paper presents a new version of kao's model to consider groups' generality, accordance with aim of comparison, while possibility of calculating inefficiency of internal units is still provided. this version due to calculating bigger amounts of efficiency is more eligible to allocate efficiency of one to several groups. for this reason a ranking method of efficient groups is presented to support proposed model. proposed models included in new version of kao's model and ranking efficient groups model were applied on data provided about supervisory sections of a bank.