The evolution of innovation system literature is scrutinized to delineate the conceptual trends over the past 30 years. We applied the Sigma index which is supposed to include not only the frontier contributions in the field but also the intellectual bases conveying transformative concepts. Our examination shows that after the establishment of the National Innovation System (NIS) as a principal framework, Regional IS literature emerged as a main branch during the period of 2002–۲۰۰۷, while Technological IS developed as the second main branch from 2007 to 2012. Surprisingly, Sectoral IS has not yet generated a separate constellation, whereas the period after 2012 mainly witnessed the emergence of Triple Helix and Agricultural IS as two new branches. The core of the literature has become classified into persistent intellectual bases (e.g. Lundvall 1992 and Nelson, 1993), diminishing pioneers (e.g. Freeman 1987; Edquist, 1997), emerging works (e.g. Hekkert et al., 2008; Bathelt et al. 2004) and fluctuating others (e.g. Carlsson, 1991; Malerba 2002). Conceptual implications are discussed at the end.

Introduction

The field of innovation studies has been recently scrutinized to examine the main contributions (Martin, 2012), disciplinary characteristics (Fagerberg et al., 2012a; Fagerberg and Verspagen, 2009), and conceptual developments (Fagerberg et al., 2012b). Other scholars have captured state of the art knowledge by bringing together major contributions in handbooks (Fagerberg et al., 2004; Hall and Rosenberg, 2010), or collections of the most important papers (Fagerberg, 2015; Martin and Nightingale, 2000). Dialogues among multiple disciplines about a topic continue to shape the Multi-disciplinary fields, while inter-disciplinary fields are those having generated concepts and approaches, including notions from contributing approaches (Bowden, 1995). Scholars engaged in those topics are interested in showing how they have produced such concepts indicating that they are transforming from a multi into interdisciplinary field (such as STS studies, Jasanoff et al., 1995; Hackett et al., 2008; Felt et al., 2017). The field of innovation studies shares a similar characteristic that has emerged in a cross section of economics of R&D and business studies (Fagerberg et al., 2012b). Among the very important and new concepts within this field, NIS might be the preeminent interdisciplinary approach (Martin, 2012), popularized in the late 1980s in a book edited by Dosi et al. (1988) containing a specific section discussing NIS in four different chapters by Richard Nelson (1988), Christopher Freeman (1988), Bengt-Åke Lundvall (1988) and Pelikan (1988).