Broken windows theory

The Broken windows theory was created by (who also conducted the Stanford prison experiment) and states that signs of neglect can encourage further neglect and destruction. It is the basis of one of the biggest theories in policing.

The experiment
The broken windows theory of policing was introduced by George L. Kelling (a fellow at the Manhattan Institute) and James Q. Wilson (of the American Enterprise Institute) in 1982.

This theory was developed based on an experiment where two cars were parked without their licence plates and their hoods up in two different urban environments, one in a poor and crime-ridden section of New York City while the other was parked in a rich neighborhood in California. The New York car was destroyed in 10 minutes while the California car lasted over a week. Then Zimbardo took a sledgehammer to the California car and it was taken apart soon after just like the New York car.

Idea in criminology
Later on, criminologists and  decided to take the Zimbardo experiment and apply it to a societal level. Their idea is that, as soon as signs of disorder appear in a neighborhood, it's only a matter of time before the neighborhood falls apart. They considered signs of disorder to be visible crimes such as drug use or prostitution, defacing the environment with graffiti and even loitering. The idea was that if you can get the police department to get these signs of disorder addressed, it will prevent bigger crimes.

This idea had a large effect in American policing policy, particularly in New York City, where William Bratton was convinced to focus on misdemeanours and turnstile jumpers and subway crime seemed to decrease dramatically. By 1994, he became the police commissioner and extended the same idea to patrolling police officers, cracking down on disorderly behaviour such as panhandling and public drinking.

Effects
Despite the glowing recommendations by various proponents, there has been little to no proof that reducing signs of disorder causes any reduction in more serious crime. In the locations it was tested in, there was a much higher crime rate due to the 1980s crack epidemic, and the effect that was thought to be from broken windows policing was actually crime reducing to its normal levels.

A later experiment looked at two groups of people, one that stayed in high crime public housing while the other was given housing vouchers to move to lower-disorder neighborhoods and compared the crime rates of the two groups. If broken windows policing was true, we would expect there to be less crime caused by those who moved out of public housing, but there was no difference between the crime rates of the two groups.

One way this policy did affect society was in discriminatory policing. With a concept as vague as disorder and with each police officer targeting what they thought constituted disorder, who was targeted and what crimes were targeted were often racially or politically motivated. The idea that minor disorderly crimes being a precursor to more extreme ones also may have encouraged police officers to see many more people as bad guys and encourage them to use minor crimes as a pretext for drug searches.