There were days upon days in New York City when not a single person was murdered in 2009. Two such stretches, in February and March, lasted nearly a week each.

There were some pockets of the city where homicide was a singular occurrence: 12 of the city’s 77 police precincts, in locations as varied as Hamilton Heights, in Upper Manhattan, and Park Slope, Brooklyn, had logged one each through Sunday.

The story line of murder in New York is one that has been undergoing constant revision since 1963, when the Police Department began tracking homicides in a way that officials now deem reliable. (Before then, homicides were not counted until they were solved.) There have been rises  the number peaked at 2,245 in 1990  and subsequent falls. But there have never been as few homicides as this year.

The city is on track, for the second time in three years, to have the fewest homicides in a 12-month period since the current record keeping system began. As of Sunday, there had been 461; the record low was in 2007, when there were 496 for the entire year.