On the historical examples of the application of zero tolerance kind of policies, nearly all the scientific studies conclude that it didn't play a leading role in the reduction of crimes, a role which is instead claimed by its advocates. On the other hand, large majorities of people who living in communities in which zero tolerance policing has been followed believe that in fact has played a key, leading role in reducing crime in their communities.[14] It has been alleged that in New York City, the decline of crimes rate started well before Rudy Giuliani came to power, in 1993, and none of the decreasing processes had particular inflection under him.[14][15] and that in the same period of time, the decrease in crime was the same in the other major US cities, even those with an opposite security policy. But the experience of the vast majority of New Yorkers led them to precisely the opposite conclusion and allowed a Republican to win, and hold, the Mayor's office for the first time in decades in large part because of the perception that zero tolerance policing was key to the improving crime situation in New York City. On the other hand, some argue that in the years 1984-7 New York already experienced a policy similar to Giuliani's one, but it faced a crime increase instead.[14]
Two American specialists, Edward Maguire, a Professor at American University, and John Eck from the University of Cincinnati, rigorously evaluated all the scientific work designed to test the effectiveness of the police in the fight against crime. They concluded that "neither the number of policemen engaged in the battle, or internal changes and organizational culture of law enforcement agencies (such as the introduction of community policing) have by themselves impact on the evolution of offenses."[14][16]
The crime decrease was due not the work of the police and judiciary, but to economic and demographic factors. The main ones were an unprecedented economic growth with jobs for millions of young people, and a shift from the use of crack towards other drugs.[14][17]
