Not all stops are created equal. Sometimes the police pull people over for traffic-safety reasons - for speeding or running a red light, for example. More nefariously, recent reports ... have shown that police departments ... have used traffic enforcement to generate fines to fund local government. But [another] kind of stop - an investigatory or pretext stop - uses the traffic laws to uncover more serious crime. Such stops (and subsequent searches) exploded in popularity in the 1990s. Pretext stops are responsible for most of the racial disparity in traffic stops in the US. Political scientist Charles Epp found that when the police are actually enforcing traffic safety laws, they tend to do so without regard to race. But when they are carrying out investigatory or pretext stops, they are much more likely to stop black and other minority drivers: black people are about two-and-a-half times more likely to be pulled over for pretext stops. The damage from a pretext stop - of a driver, a pedestrian, a loiterer - doesn't end with the stop itself. The pretext-stop regime ... propels disparities in the rest of the criminal justice system. By ... 2000, we had been steadily, incrementally, building the punitive criminal justice system we still live with today. Most of the pieces - the aggressive prosecutions and policing, longer sentences, prison-building, collateral consequences of convictions such as losing the right to vote or the chance to live in public housing - had been put in place. The years since [have] been primarily dedicated to maintaining ... that basic architecture.