Laws such as 0.08 blood alcohol content, open container, and license revocation provide a policy framework for reducing drinking and driving. Drinking and driving behavior is difficult to assess; unlike property and violent crimes, where incidence statistics can approximate behavior, most drink-driving trips go undetected. The authors develop a novel measure of drink-driving propensity by estimating an item response model using national survey data. The authors illustrate their measures in the aggregate and as they relate to law enforcement efforts in the American states. (Contains 4 tables, 4 figures and 8 notes.)