Determining Left and right Returns to Scale (RTS) and RTS sustainability by using linear programming problems based on simultaneous changes in inputs and outputs

Determining the type of returns to scale (RTS) and identifying stability region for RTS of evaluating unit are appropriate abilities for forecasting the future the unit when its size is changed. This paper aims to introduce RTS sustainability of frontier decision making units (DMUs) in data envelopment analysis (DEA). Based on the importance of RTS in relation to decisions of managers, different methods have been proposed to define RTS and determine the type RTS. Research on RTS led to a more general categorize for the type of RTS, named left RTS (L-RTS) and right RTS (R-RTS). All of the methods in evaluating L-RTS and R-RTS have presented parametric programming problems which are non-linear programs, naturally. In tis situation, researchers are facing the challenge to determine the value of parameters. In order to survey this limitation, the present paper suggests linear programming problems. Moreover, the proposed models with minor changes are appropriate tools for determining the RTS sustainability for evaluating unit.