en عمومى General پژوهشي Research <span style="font-size:11pt"><span style="line-height:normal"><span style="unicode-bidi:embed"><span style="font-family:Calibri,sans-serif"><span lang="EN-US" new="" roman="" style="font-family:" times="">Network Data Envelopment Analysis (DEA) has attracted considerable attention in both methodological research and practical applications of performance evaluation. This paper investigates a fundamental class of network DEA models, namely the two-stage network framework. In conventional DEA, where the production process is viewed as a &ldquo;black box,&rdquo; returns to scale (RTS) plays a critical role in guiding managerial decisions on whether to expand or contract operations. This study extends the traditional concept of RTS to a two-stage network by examining input variations from three perspectives: stage 1, stage 2, and the overall system. The proposed approach employs parametric analysis to capture how these variations affect the relationships among inputs, intermediate measures, and final outputs. To ensure practical applicability, the method can be implemented through existing linear programming formulations and remains computationally feasible even for larger-scale problems. In addition, we develop a linear programming model that supports central managers in coordinating resource allocation across different stages, thereby achieving system-wide improvements. A numerical example illustrates that RTS classifications at the system and sub-process levels may diverge, offering distinct insights into pathways for enhancing productivity.</span></span></span></span></span> Data Envelopment Analysis, Returns to scale, Network 17 42 http://ijorlu.lahijan.iau.ir/browse.php?a_code=A-10-596-1&slc_lang=en&sid=1 T. Mollaalizadeh Koloukhi t.m.alizadeh@gmail.com 10031947532846002223 10031947532846002223 No Department of Mathematics, N.T.C., Islamic Azad University, Tehran, Iran A. Mostafaee a_mostafaee@iau-tnb.ac.ir 10031947532846002224 10031947532846002224 Yes Department of Mathematics, N.T.C., Islamic Azad University, Tehran, Iran S. Saati s_saatim@iau-tnb.ac.ir 10031947532846002225 10031947532846002225 No Department of Mathematics, N.T.C., Islamic Azad University, Tehran, Iran