Here is a data-dense (NYC and national) article from the NYT in regard to the 2008 knife stats. There is much more at the link than what I've excerpted.

It would be important to know more about these knife murders -- demographics on the perps (i.e. youth, gang members) where they occurred (domestic disputes, schoolyard, muggings, rapes).


http://www.nytimes.com/2009/04/28/nyregion/28knives.html

Knife Killings in City Increased 50 Percent in 2008

By CHRISTINE HAUSER
Published: April 27, 2009


In 2008, even as gun killings fell, the number of killings committed with knives or other “cutting instruments” rose 50 percent in New York City, the Police Department said: to 125 from 83. Some other large cities saw no such increase last year, and police officials and experts are at a loss to explain what is either a new trend or a spike.

“It is hard to say with certainty what accounts for the increase,” said Paul J. Browne, the chief spokesman for the New York Police Department.

Law enforcement officials suggest that killings with knives or other common instruments, box cutters, screwdrivers or even corkscrews, are hard to combat. These tools are easy to obtain and conceal: anyone can walk into a store and buy one, or open a kitchen drawer and grab one.

National statistics show a general decrease in knife killings in the five-year period from January 2003 to December 2007.