DRAFT Assessing State Nuclear Weapons Proliferation: Using Bayesian Network Analysis of Social Factors 1 By: Garill Coles, Alan Brothers, Jarrod Olson 2 , and Paul Whitney ABSTRACT: A Bayesian network (BN) model of social factors can support proliferation assessments by estimating the likelihood that a state will pursue a nuclear weapon. Social factors, including political, economic, nuclear capability, security, and national identity and psychological factors may play as important a role as more physical factors in whether a State pursues nuclear weapons. This paper illustrates how Bayesian reasoning can be used to combine evidence that supports proliferation assessment for a generic case of a would-be proliferator State . Theories and analysis by political scientists can be leveraged in a quantitative and transparent way to indicate proliferation risk. BN models facilitate diagnosis and inference in a probabilistic environment using a network of nodes and acyclic directed arcs between the nodes whose connections, or absence of, indicate probabilistic relevance, or independence. We propose a BN model that uses information from both traditional safeguards and the strengthened safeguards associated with the Additional Protocol to indicate countries with a high risk of proliferating nuclear weapons. Such a model could be used in a variety of applications such a prioritization tool and as a component of state safeguards evaluations. This paper will discuss the benefits of BN reasoning, the development of Pacific Northwest National Laboratory’s (PNNL) BN state proliferation model, and how the model could be employed as an analytical tool. Introduction In 1962, John F. Kennedy famously predicted that the world faced a cascade of nuclear weapons proliferation as nuclear technology and knowledge continued to spread. This prediction mirrored the common belief in the “Technological Imperative” common at the time, where acquisition of nuclear energy technology would inevitably yield nuclear weapons technology. Fortunately, this proved to be an inaccurate forecast. Political scientists have since continued to examine the root causes of proliferation and build frameworks for understanding nuclear weapons proliferation. However, one commonly acknowledged shortcoming of existing studies of proliferation is that they rely on historical precedent. They identify when a state is following the same path as historic proliferators, but they may not be able to predict the next wave of proliferators. In 2009, Alexander Montgomery and Scott Sagan identified key shortcomings of proliferation studies. 3 They noted that data are scarce about nuclear weapons and it is difficult to 1 PNNL-SA-72126 2 Contact author: 1100 Dexter Ave N. Suite 400, Seattle, WA 98109. jarrod.olson@pnl.gov 3 Montgomery, Alexander H., Scott Sagan. The Perils of Predicting Proliferation. Journal of Conflict Resolution, 4 February, 2009, http://online.sagepub.com/ doi: 10.1177/0022002708330581