Inputs/outputs estimation in DEA when some factors are undesirable

In this paper we investigate inputs/outputs estimate in the presence of undesirable factors. We discuss such questions: suppose some outputs (inputs) are undesirable and among a group of decision making units (DMUs) a DMU changes (increases and decreases simultaneously) some of its input (output) levels, how much outputs (inputs) could the unit change such that its efficiency index remains unchanged? To solve the problem we propose a multiple objective linear programming (MOLP). Our MOLP model could estimate input/output levels, regardless of the efficiency or inefficiency of the DMU. We propose necessary and sufficient conditions for inputs/outputs estimation. A numerical example is given. 2003 Elsevier Inc. All rights reserved.