I recently had a discussion with a very intelligent woman, a Ph.D fresh from an Ivy League university. We met after the third Clinton-Trump debate, so the conversation naturally turned to race in America, a topic about which my interlocutor felt strongly. She explained that the United States’ criminal justice system is an oppressive apparatus of state racism. Mass incarceration, she told me, is in large measure the product of a war on drugs that unfairly targets African Americans. She painted a picture of prisons overfilled with African American men locked away for nonviolent drug offenses. She was convinced that the US criminal justice system requires dramatic reform or complete dismantling. My question for her was simple: approximately what fraction of US prisoners are incarcerated for possession — as opposed to pushing or smuggling? She did not know. It is worth pausing to reflect on this. There is hardly a fact about the war on drugs that could be more basic. But my interlocutor did not know the answer to this simple question, despite her …