Much of the current argument about whether to legalize various currently illicit drugs is conducted at a high level of abstraction (morality and health vs. liberty and public safety). The details of post-prohibition policies are barely mentioned and concrete outcomes are either ignored or baldly asserted without any careful marshaling of fact and analysis. But it is possible to try to predict and evaluate– albeit imperfectly – the likely consequences of proposed policy changes and to use those predictions to choose systems of legal availability that would result in better, rather than worse, combinations of gain and loss from the change.