What the heck is NYC doing so right to reduce murders, and why can't Chicago replicate it?

The question in the title of this post is prompted by this notable little news item from the New York Times headlined "New York Today: Murder Milestone." Here are the encouraging details:

The city’s murder rate keeps plummeting. So far this year, it’s down 26 percent, officials said.

If that trend holds, it would be the biggest one-year drop yet. And last year had the fewest murders in at least 50 years.

We asked the police bureau chief of The New York Times, Joseph Goldstein, to explain the decline. Some credit goes to a focus by the police on informal youth gangs known as crews, Mr. Goldstein told us.

The police, he said, “make the point that murders attributable to street violence are down even more significantly.” Last week, there were no murders at all.

The drop comes even as officers are doing only about half as many stop-and-frisks as they did at the beginning of last year.

Michael Jacobson, a former city correction commissioner and now a sociology professor at City University of New York, noted that last year’s total of 419 murders was down from 2,245 in 1990.

“If you asked any criminologist 20 years ago, ‘Can it go from 2,200 to 400?’ they would have thought you were insane,” he said. “But if it can go from 2,200 to 400, why can’t it go from 400 to 200?”

This wonderful reality should be celebrated by everyone, though it ought to be especially cheered by those who claimed that recent violent crime declines in the NYC were attributable primarily to very aggressive stop-and-frisk policies and practices. Also of note, especially for sentencing fans, is that this continuing decline in NYC murders is taking place within in a state without the death penalty and with a relatively low (and recently declining) prison population.

Of course, correlation does not mean causation, and a major city in a major state (Chicago, Illinois) is having continuing big problems with violent crime during the same period. Indeed, while folks in Chicago are now very busy having an interesting and robust debate over whether a law proposing mandatory minimum sentences for gun possession is a good way to fight violent crime (as documented in this effective op-ed and this prior post), I wonder if they might use their time and energy more effectively by trying everything they can to replicate everything that folks in NYC are doing lately.

Some related posts on modern crime rates, especially in urban areas: 

• Is there really a simple explanation for record-low homicide rate in NYC (or the increase in Chicago)?
• So far in 2013, more investment in cops means less homicides in Chicago
• Is the great US crime decline now finally over?: BJS reports crime up in 2011
• FBI reports crime was down yet again in 2011 (though BJS said it was up)
• Should we thank unleaded gas and the EPA for the great modern crime decline?
• Still more (and still puzzling) crime rate declines reported by FBI
• Effective Washington Post commentary talks up great (and still puzzling) crime decline