John Mueller is a political scientist at Ohio State University and at the Cato Institute. He is the author, co-author, or editor of 18 books and hundreds of scholarly and popular articles. His research areas include international relations, security studies, risk analysis, public opinion, foreign policy, terrorism and counterterrorism, and dance history. Mark G. Stewart is Professor of Civil Engineering at The University of Newcastle, Australia. He has more than 25 years of experience in probabilistic risk and vulnerability assessment of infrastructure and security systems. His expertise in risk assessment is applied to a wide range of threats and hazards most notably terrorism and climate change.