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on exploration, and major power status an enormous relationship with acquisition, albeit
in both cases only in the tens of thousands of percent. With the possible exception of the
three exceptionally large results reported above, the other results appear plausible, and
consistent with other work I have conducted on the determinants of nuclear weapons
proliferation.
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Note that the effect of having an enduring rival acquire nuclear weapons
is substantial, increasing states’ risk of exploring nuclear weapons by more than 400
percent, in other words, making them more than four times more likely to explore.
6. Discussion and conclusion
Are states whose rivals proliferate more likely to do so themselves? The findings
presented above provide robust support for a nuanced hypothesis: States whose rivals
proliferate are substantially more likely to explore nuclear weapons options and engage in
other low-level proliferation behavior, but at least on average, no more likely to launch
nuclear weapons programs or to acquire nuclear weapons. These findings are
exceptionally robust across a broad range of models. As noted above, this paper presents
only one facet of the dissertation project in progress on this topic. Additional quantitative
analysis, not included here, explains modest variation in reactive proliferation outcomes
by using interaction coefficients to examine the relationship between states’ likelihood of
reactively proliferating and the intensity of rivalry with the initial proliferant, the degree
of proliferation behavior engaged in by that proliferant, the potential respondent’s level
of technological development, and the potential respondent’s access to a security
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Philipp C. Bleek, “Why Do States Proliferate? Quantitative Analysis of the Exploration, Pursuit, and
Acquisition of Nuclear Weapons” in William Potter (ed.), Forecasting Proliferation: The Role of Theory
(Stanford, CA: Stanford University Press, forthcoming winter 2010).
Convention