What is the state of the quantitative literature on risk factors for radicalization and recruitment to terrorism?

Terrorism research has become a field of increasing interest and importance over the last few decades. Since the events of 9/11, the number of publications in the field has increased exponentially. Despite the explosion in terrorism research, reviews of the literature have consistently bemoaned the dearth of empirical evidence (Silke 2001, 2007, 2009; Sageman 2014). Among the most prominent explanations given for the findings that as little as 3-5% of research is based on any form of empiricism, is the continued absence of definitional clarity and consensus. Scholars also refer to the lack of original data, and a tendency for terrorism research to reuse the same data sets many times over, as one of the primary limitations of the literature (Schuurman and Eijkman 2013). Such criticisms were summarized in Sageman’s (2014) infamous article on the ‘stagnation of terrorism research’.