Data enveleopment analysis and negative imput data

Data envelopment analysis (DEA) is used as a tool for technical efficiency evaluation of decision- making units. The units are compared with each other, which means to compare inputs, outputs and evaluate their efficiency. In case of non-efficiency unit, we can ordain necessary changes for achievement of efficiency using the DEA methods. One of the necessary conditions for using basic DEA methods is non-negativity. If that condition is not satisfied, it is not possible to use the basic DEA methods and common software. Then, it is necessary to create a new tool.