Over the past 20 years, authorities have made more than a quarter of a billion arrests, the Federal Bureau of Investigation estimates. As a result, the FBI currently has 77.7 million individuals on file in its master criminal database—or nearly one out of every three American adults.

In 2011, the most recent year for which figures are available, the Bureau of Justice Statistics put the number of full-time equivalent sworn state and local police officers at 646,213—up from 531,706 in 1991.

A crackdown on what seemed like an out-of-control crime rate in the late 1980s and early 1990s made sense at the time, says Jack Levin, co-director of the Brudnick Center on Violence and Conflict at Boston’s Northeastern University.

“Zero-tolerance policing spread across the country after the 1990s because of the terrible crime problem in late ’80s and early 1990s,” says Mr. Levin.

The push to put an additional 100,000 more officers on the streets in the 1990s focused on urban areas where the crime rates were the highest, says Mr. Levin. And there has been success, he says, as crime rates have fallen and the murder rate has dropped.

But as a consequence, “you’ve got these large numbers of people now who are stigmatized,” he says. “The impact of so many arrests is catastrophic.”