The math of terrorist threats

Not worth factoring in to your calculations.

Jane Galt, living in New York, asks for an odds calculation with respect to riding the subway in the face of a terrorist threat.

Let’s imagine that a successful subway attack would kill or injure 100 people, and that there’s one chance in 50 of an attack on any given day when heightened warnings are in place. With an average weekday ridership of 4.5 million, that puts the probability of being hurt or killed at about 1 in 2 million, or, in technical statistical language, approximately fuhgettabadit.

The individually rational response to all such threats is identical with the socially optimal response: go about your business and let the cops worry about catching the bad guys. The mass media, by falsely dramatizing all such warnings, make our civilization more vulnerable to terrorist threat than it needs to be.

Author: Mark Kleiman

Professor of Public Policy at the NYU Marron Institute for Urban Management and editor of the Journal of Drug Policy Analysis. Teaches about the methods of policy analysis about drug abuse control and crime control policy, working out the implications of two principles: that swift and certain sanctions don't have to be severe to be effective, and that well-designed threats usually don't have to be carried out. Books: Drugs and Drug Policy: What Everyone Needs to Know (with Jonathan Caulkins and Angela Hawken) When Brute Force Fails: How to Have Less Crime and Less Punishment (Princeton, 2009; named one of the "books of the year" by The Economist Against Excess: Drug Policy for Results (Basic, 1993) Marijuana: Costs of Abuse, Costs of Control (Greenwood, 1989) UCLA Homepage Curriculum Vitae Contact: Markarkleiman-at-gmail.com