Homicides in New York City have plummeted 18 percent in 2012 over the same period last year and, with three months left in the year, are at a rate among the lowest seen in the post-World War II period, records show.

There were 319 homicides in the city, compared with 389 in the same period last year, as of Sept. 30, police officials said Monday. If the trend continues, the city may have just over 400 killings this year.

NYPD Commissioner Ray Kelly said homicides could come in at a number not seen in 50 years since the Kennedy administration.

But privately, police officials think that the slayings may actually drop below what occurred during the waning days of President Dwight D. Eisenhower's tenure.

The drop in homicides follows a news conference Thursday during which Mayor Michael Bloomberg said shootings in the city have also fallen.

Kelly is scheduled Tuesday to tell a meeting of international police chiefs in San Diego that a new NYPD initiative dubbed Operation Crew Cut aimed at informal street gangs could drive homicides and shootings even lower.

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"We're hoping that by focusing more resources in a coordinated, thoughtful way on these crews we'll reduce violent crime in New York City even further. That's because crews are responsible for no less than 30 percent of shootings in New York City," said Kelly, according to a copy of his speech.

While the city has had seen a drop in homicides, a spate of shootings over the summer led to a number of killings around playgrounds.

They included was the slaying of 4-year-old Lloyd Morgan who was hit by gunfire in July while watching a basketball game in the Bronx. In June, three died and seven were wounded in separate shootings.

Police and criminologists credit several factors for the drop, including concentrations of officers in crime hot spots, better trauma treatment at local hospitals, and what Ohio State professor Randolph Roth said were historic changes in society.

Among the changes were a belief in the stability of government, patriotism and racial solidarity, perhaps brought on by the Barack Obama's election in 2008, said Roth, who teaches history and sociology.

The rate of homicides -- the number of killings per 100,000 people -- has also dropped as the city population increased. As of Sunday, the murder rate in New York was 3.86 per 100,000, with a population of 8.24 million.

In 1940, the rate was 3.68, per 100,000, when the city saw at least 275 homicides and had a population of 7.45 million.