Why is Chicago struggling with gun violence? N.Y. might have answers.

At first glance, it might appear that Chicago is doing many things right in its fight against gun violence.

Strict gun laws prohibit the purchase of guns within city limits, ban the possession of assault weapons, and call for steep fines if stolen or lost guns are not reported to police. Moreover, the Chicago Police Department seized 7,400 guns used in crimes in 2012 – more than twice what New York City did, for example.

Yet Chicago is in the midst of its worst period of gun violence in years. Its 513 homicides last year was a four-year high, and last month’s 42 homicides were the most in a January since 2002. Meanwhile, much larger New York had only 414 homicides in 2012 – an all-time low. If it had Chicago’s murder rate, New York would have totaled more than 1,400.

Both cities have tough gun laws, and both face the problem of weapons used in crimes being brought in from outside their borders. But New York has distinguished itself by its anti-gang program. Though experts acknowledge that New York and Chicago are different cites with different factors in play, they point to New York’s work in reducing gang violence as a game-changer.

“If you remove gang-related incidents from the Chicago homicide statistics, the homicide rate involving normal citizens is much lower,” says James Alan Fox, a criminologist at Northeastern University in Boston.

New York’s experience suggests that Chicago’s emphasis on seizures, while not necessarily counterproductive, might not be the most effective tool for lowering its homicide rate.

“It’s certainly good to get guns off the street and the more guns you can acquire can’t hurt. But in places like Chicago where you can go outside the city line and buy all the guns you want, it’s not clear that [gun seizures] have any demonstrable impact on crime,” says Richard Berk, a criminologist at the University of Pennsylvania in Philadelphia.

For one, keeping track of guns is notoriously difficult. Straw gun purchasing, in which guns are purchased legally but are passed to another person for criminal purposes, is a problem in every major city. In Chicago, 20 percent of the guns used to commit crimes between 2008 and March 2012 originated in the suburb of Riverdale, Ill., because of a single store there – Chuck’s Gun Shop, according to the University of Chicago Crime Lab. The store owners say they follow federal and state laws and are not legally responsible for how, or where, the guns they sell are used.

The state of New York faces a similar problem. Some 84 percent of gun crimes were carried out with guns purchased over the state border, according to the US Bureau of Alcohol, Tobacco, Firearms and Explosives.

“Coordination [of gun laws] is a big problem, not just because there are so many different philosophies of government, but also because of the nuts and bolts of enforcement,” says Harold Pollack, a co-director of the University of Chicago lab.

What does separate Chicago from New York City is its gang activity. Chicago leads the country in terms of the number of individuals who are direct gang members or involved in gang factions, which are splinter groups associated with larger criminal organizations. There are an estimated 70 to 100 gangs in the Chicago metropolitan area with a membership of between 68,000 and 150,000, according to the 2012 Chicago Crime Commission. New York gang membership is about 22,000, reports the National Gang Intelligence Center in 2009.

Professor Fox of Northeastern says Chicago has a larger minority underclass and harsher socioeconomic conditions than New York City, which makes it difficult to compare the homicide rates of both cities.

“They’re different cities, they’re different in terms of demography, they’re different geographically,” he says. “These are big factors.”

But in October, New York Police Commissioner Ray Kelly announced “Operation Crew Cut,” which doubled the size of its gang division from 150 to 300 detectives. It is indicative of how New York has become a national leader in taking on gangs, experts say.

“One of the most interesting stories in policing is why New York has not experienced gang problems to the extent that other cities like Chicago and L.A. have,” Chuck Wexler, executive director of the Police Executive Research Foundation Forum, told ABC News. “Kelly's recognition of this emerging issue of gang activity in New York and his comprehensive approach using social media will be watched closely.”

Representatives from the Chicago Police Department did not respond to numerous e-mails and phone messages seeking interviews Friday.

For now, Chicago Mayor Rahm Emanuel has announced he is reassigning 200 officers from desk duties to street patrols of the city’s West and South Sides, where gun violence is highest. That is in addition to the 500 new officers he wants hired in 2013.

Last month, New York Mayor Michael Bloomberg swore in 830 recruits.