Mark Bell’s article (2016) is a welcome contribution to the unavoidable task of evaluating a
research program that exhibits the problems he identifies: the failure of most quantitative
studies to offer strong explanations for proliferation patterns, and their inability to predict
out-of-sample cases. His findings resonate with those of other proliferation experts. The
existing quantitative literature, argues Bell, produces more tentative findings than scholars
typically understand. We concur fully with the first part of the last sentence but believe that
the broader community of experts typicallydoesunderstand the serious limitations of most
quantitative studies (and qualitative ones) on this topic.