Data on illicit drug purity and prices are invaluable but challenging. Academic purists argue they are unsuitable for economic analysis [Manski, C.F., Pepper, J.V., Petrie, C.V., 2001. Informing America's Policy on Illegal Drugs: What We Don't Know Keeps Hurting Us. National Academy Press, Washington, DC], but in practice they are used frequently [ONDCP, 2001a. What America's Users Spend on Ill...