Probably the biggest driver of this growth has been ever-harsher drug penalties. In response to the crack epidemic of the 1980s, Congress and state legislatures began passing laws that meted out mandatory-minimum sentences for drug-related crimes. These were intended to help nab major traffickers, but the sentences were triggered by the possession of tiny quantities of drugs: five grams of crack, for instance, resulted in a mandatory-minimum sentence of five years. Conspiracy laws made everyone involved in a drug-running operation legally liable for all of the operation’s activities: a child hired for a few dollars a day to act as a lookout at the door of a crack house was on the hook for all the drugs sold in that house and all the crimes associated with their sale. These sorts of laws kept America’s prison population growing even as its crime rate declined.