Ebrahim Souzanchi Kashani - Graduate School of Management and Economics, Sharif University of Technology
Saeed Roshani - Phd Student, School of Management, Allameh Tabatabaei University

The evolution of innovation system literature has been scrutinized in order to delineate the conceptual trends overthe past 20 years. We applied the Sigma index that is supposed to include not only the frontier contributions in thefield that are getting increasing citations over time; but also the intellectual bases conveying transformativeconcepts. Our examination shows that after establishment of NIS as a principal concept with Freeman (1987),Lundvall (1992) and Nelson (1993) as the most important works, RIS literature has emerged in the period of 2002-2007 as the imperative and novel concept while after that, TIS is regarded as the pivotal conceptual innovationwithin the field. Surprisingly, although both of them are forming their specific clusters, SIS could not establish itsown constellation, nor is it being regarded at the center of attention during the past two decades. Analyzing newtrends show that triple helix is an emerging concept whereas recent attentions are now being paid towards someolder concepts such as diffusion of innovation as well as absorptive capacity.

innovation systems, NIS, RIS, TIS, SIS, scientometrics