Multiple solutions identification in data envelopment analysis

This paper addresses the problem of analyzing the results of a benchmarking process in which the efficiency of a set of Decision Making Units (DMUs) is evaluated via Data Envelopment Analysis (DEA). Because of the special structure of DEA linear programs, degeneracy often occurs and optimal solutions are not necessarily unique. This lack of uniqueness does not affect the efficiency evaluation of DMUs, but it may play a critical role in the interpretation of additional information provided by DEA models. Focusing on virtual inputs and outputs analysis, we suggest in this paper a two stage linear programming approach.