“…Because confounding is a potential threat to inference whenever the causal variable is itself caused by something else, and because virtually everything in social science is caused by something else, endogeneity is ubiquitous. For instance, democracy is said to cause peace (Maoz and Russett, 1993;Bueno de Mesquita, Morrow, Siverson and Smith, 1999;Bausch, 2015), but democracy itself is thought to be endogenous to such variables as GDP, trade, and (most troublingly) peace (Gates, Knutsen and Moses, 1996;Reuveny and Li, 2003). Similarly, military alliances are widely accepted as a tool that can reduce the risk of conflict (Leeds, 2003;Johnson and Leeds, 2011;Benson, 2011;Fang, Johnson and Leeds, 2014), but both alliance formation and conflicts are driven by the (typically unobserved) interests and security environment of the states involved.…”