Murders in New York have dropped to their lowest level in over 40 years, city officials announced on Friday, even as overall crimes increased slightly because of a rise in thefts — a phenomenon based solely on robberies of iPhones and other Apple devices.

There were 414 recorded homicides so far in 2012, compared with 515 for the same period in 2011, city officials said. That is a striking decline from murder totals in the low-2,000s that were common in the early 1990s, and is also below the record low: 471, set in 2009.

“The essence of civilization is that you can walk down the street without having to look over your shoulder,” Mayor Michael R. Bloomberg said.

Mr. Bloomberg acclaimed the accomplishment during a graduation ceremony for more than 1,000 new police officers at the Barclays Center in Brooklyn. He attributed the low murder rate to the department’s controversial practice of “stop, question and frisk,” in which people are stopped on the street and questioned by officers, and aggressive hot-spot policing, in which officers are deployed to areas with crime spikes. Shootings are also down for the year so far. The number of murders is the lowest since 1963, when improvements in the recording of data were made.