Does 'Stop and Frisk' Reduce Crime?

There have been no randomized, controlled experiments to test the efficacy of "stop and frisk." It is possible, however, to compare New York’s record in lowering crime with that of other cities that do not practice its proactive style of policing.

The New York Police Department’s critics favor High Point, N.C., Boston and Chicago as models the department should emulate. Boston’s crime rate is 4,107 crimes per 100,000 residents; High Point’s is 5,212 per 100,000 residents; New York’s is 2,257 per 100,000 residents. In 2010, Chicago’s murder rate was more than double that of New York.

San Diego has been another frequently invoked foil to New York. Franklin Zimring, a law professor at the University of California, has calculated that New York’s homicide rate would have been 73 percent higher in 2007, had New York’s black residents been killed with the same frequency as blacks in San Diego. New York’s 80 percent drop in crime since the early 1990s is twice as deep, and has lasted twice as long, as the national average, as Zimring shows in his recent book, "The City That Became Safe."

Only New York’s policing revolution, which began in 1994 and seeks to prevent crime before it happens, explains the distinction. Poverty and unemployment were higher in New York than in the nation as a whole over the last decade and a half. New York’s rates of drug use, income inequality and student failure did not go down.

What has changed is the city’s style of policing. Since 1994, the police department has deployed officers to areas where law-abiding residents were being most victimized and has asked those officers to intervene in suspicious behavior before a crime happens. Stop and frisk has been a vital part of that approach. David Weisburd, a George Mason University criminologist, found in a recent unpublished paper that those stops have been targeted with pinpoint precision to the street segments where crime is highest.

One purpose of stop and frisk is to deter criminals from carrying guns, in order to minimize spur-of-the-moment shootings. That deterrence has taken place. Street gangs now keep "community guns" in communal locations rather than on their person, to avoid a gun possession arrest if they are stopped. The city’s astounding homicide drop - 82 percent from 1990 to 2009 - is driven by a decline in gun crime, which disproportionately affects black males. In 2011, guns were used in 61 percent of all homicides, but 86 percent of black males between the ages of 16 and 21 killed that year died from gunfire, according to N.Y.P.D. data.

Being stopped when you are innocent is an infuriating, humiliating experience. New York’s officers need to better explain to stop subjects why they were accosted. And if a more powerful method of deterring crime is developed, the N.Y.P.D. should and would adopt it. But for now, New York’s most vulnerable residents enjoy a freedom from assault unknown in any other big city, thanks to the N.Y.P.D.’s assertive style of policing.

This piece originally appeared in New York Times Room for Debate