NYC is part of general crime trends in the US. The pits were the late '70's and'80's. The nationwide crime rate started to decline. Some broad-gauged explanations included: ageing population (smaller percentage of the most dangerous-aged kids); substitution of heroin for the more violence-inducing crack cocaine; better economy (in the 90's). But there's no denying that NY improved first and most dramatically thanks to mayor Giuliani and police chief Bratton. They aggressively pursued a policy of having the cops go after "quality of life" crimes that had been ignored earlier: turnstile-jumping, 3-card monte street games, low-level drug sales, littering, loud radios, etc. Sure enough: a huge number of those QWL offenders turned out to have outstanding warrants, or were suspects in major felonies. Giuliani also demanded that the Sanitation Dept. start moving aggressively on littering. Result: cleaner, safer streets.