I was thrilled last week to open my copy of Science and find a study confirming the “broken window” theory of crime: people are more likely to commit a crime when they are surrounded by trash, graffiti, vandalism, etc. – signs that other people are not obeying the law either. The theory has been around since the early 1980s and was a cornerstone of New York City’s successful campaign to reduce crime, but until now no one has confirmed that the environment could cause an increase in criminal behavior (instead of merely being correlated with it).
In one experiment, the authors attached fliers to bicycles in an alley with no trash can and tracked how many people littered the flyers. The first day the alley had no graffiti and about a third of the bicyclists littered; the second day the alley had graffiti and over two thirds of the bicyclists littered. “Eh,” you say, “Littering… That’s barely a crime.” (You pig!) They ran another experiment with a 5 euro note sticking out of a mailbox; 13% stole it without litter around and 23% stole it with litter around.
A short review (full text is pay-only):
Reducing crime isn’t quite as simple as sending in the street cleaners a little more often, but this and other studies show that relatively cheap and easy campaigns to reduce public disorder can have a big payback. From the review:
A Harvard University study, reported earlier this year, found that scrupulous “situational prevention” in troubled neighborhoods in Lowell, massachusetts – in particular, adding policing and cleanup – was more effective than social services or law enforcement in maintaining order.
(Not sure what the difference between “added policing” and “law enforcement” is, but I’m guessing it’s police offers hanging around vs. police officers responding to incidents.)
On a related note, I recently found myself in the bizarre position of having to argue about whether crime in New York City has been significantly reduced over the last few decades. The answer is an unequivocal yes; in 2007 the number of homicides was 496, down from a high of 2245 in 1990, and the lowest since 1961. These numbers underestimate the improvement since they don’t take into account the increase in population from 7.3 million in 1990 to 8.3 million in 2007. I scraped these statistics from Wikipedia, but you can get a lot more data from the Bureau of Justice Statistics web site.