Cracking down on minor disorder ('broken windows') sharply cuts serious crime.
Verdict: contested
Visible disorder can spread disorder, but the leap to aggressive policing cutting serious crime is not well established.
What the evidence shows
The 'broken windows' theory holds that visible signs of disorder invite more disorder and eventually serious crime, so aggressively policing minor offences should prevent big ones. It shaped policing in New York and beyond in the 1990s.
The two links must be judged separately. Field experiments by Keizer et al. (2008) support the first link: people littered and even stole more amid signs of disorder, so disorder does spread. But the policy leap — that order-maintenance policing causes large drops in serious crime — is contested. Harcourt & Ludwig (2006) re-examined the New York evidence and a five-city relocation experiment and found little support for a broken-windows effect on serious crime, arguing the 1990s crime drop had other causes. Disorder matters; aggressive misdemeanour enforcement as a crime cure is not well supported.
Sources
Keizer, K., Lindenberg, S., & Steg, L. (2008). The spreading of disorder.
Science, 322(5908), 1681–1685
In field experiments, visible disorder (graffiti, litter) roughly doubled rates of littering and minor theft — disorder begets disorder.
DOI: 10.1126/science.1161405 →Harcourt, B. E., & Ludwig, J. (2006). Broken windows: New evidence from New York City and a five-city social experiment.
University of Chicago Law Review, 73(1), 271–320
Re-analysis found little evidence that broken-windows policing reduced serious crime in New York or in a five-city experiment.
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