“…Hence, these individuals worked as brokers between their organization and the migrants, made use of their pre-existing social ties, and thereby recruited them for their activities. And, in fact, the policy diffusion literature on transfer across national borders consistently emphasizes that learning and emulation can occur under those circumstances (Simmons and Elkins, 2004;Elkins and Simmons, 2005;Simmons, Dobbin and Garrett, 2008;Plümper and Neumayer, 2010;Gilardi, 2010Gilardi, , 2012) -learning and emulation facilitate overcoming the collective action problem of mobilization (see e.g., Gleditsch and Rivera, 2015). Finally, an analysis of 212 perpetrators of terrorist acts by the Nixon Center (Leiken, 2004, p.43) further supports these patterns: "they are all associated exogenously to their role in the attacks.…”