Some readers have asked whether the population of American prisons is large because we lock up so many drug users. It is true that the proportion of inmates described as drug offenders has gone up dramatically, but as Jonathan Caulkins and Mark Kleiman point in their essay in Understanding America, very few are in prison because of drug possession. Many are either major dealers or plead down to a drug possession charge in order to avoid being convicted of a more serious offense. There are more than one million arrests every year for drug possession, but very of them result in prison or jail time. Cannabis possession, when it is punished at all, is typically with a fine or probation.