Something dramatic happened in New York City in 1994: a lot of people stopped committing crimes, especially violent ones. The reduction in the number of persons committing murders, for example, while not unprecedented,' was extraordinary. Since 1994, a debate has raged about why this happened. Putting our position up front, we believe the police played an important, even central, role in getting people to stop committing crime in New York City. Despite arguments to the contrary,' no evidence exists that the substantial drops in crime in New York City, especially the initial ones when one of the authors of this paper, William Bratton, was commissioner, were the result of economic change, changes in drug use patterns, or demographic changes. Arguably, New York City's economy, drug use patterns, and demography might be different now in 1998. Unemployment was at 10% the month Bratton took over the New York City Police Department (NYPD) (January 1994) and at 8.7% when he resigned (April 1996)-hardly a booming economy.3 And remember as well, the initial reductions in crime were so steep that by August of 1995-three years ago, but only twenty months after Bratton took office-New York maga-