And while rapes were down from last year by one, to 1,417, misdemeanor sex crimes — a catchall for various types of misconduct that includes groping — ticked up 9.3 percent to 3,585 so far.
The lower homicide numbers are still preliminary — and include one announced on Wednesday night — but they jibe with large drops in killings in major cities like Chicago and Detroit, while contrasting with sizable increases in killings in smaller cities like Charlotte and Baltimore.
The city today is a far cry from what it was when Mr. Bratton arrived in 1990 to become the head of the then-separate Transit Police. Not only were there 2,245 killings that year, but there were more than 527,000 major felony crimes and more than 5,000 people shot. Shootings have plunged to 774 so far this year, well below last year’s record low of 998. And for the first time, fewer than 1,000 people have been hurt by gunfire: 917 as of Sunday.
The continued declines are a boon to Mr. de Blasio, a Democrat elected on promises of police reform — promises that prompted warnings of mayhem to come by his opponents in 2013. But the opposite has happened, putting him on stronger footing as he pivots to a second term with a Police Department transformed to exercise greater restraint as it focuses on building trust in the city’s neighborhoods.
Franklin E. Zimring, a professor at University of California, Berkeley, School of Law, said the downturn was an “astounding achievement,” but it raised another question: How long and low will crime fall?
“We don’t know when we’ve exhausted the possibilities of urban crime decline, and we won’t know unless and until New York scrapes bottom,” said Mr. Zimring, who analyzed the first 20 years of New York’s historic crime reduction and expounded on it in a book.
Mr. de Blasio and the police commissioner, James P. O’Neill, credit recent drops in crime to the Police Department’s emphasis on going after the relatively small groups of people — mostly gangs and repeat offenders — believed to be responsible for most crime, while also building relationships in communities where trust has been strained.
Mr. Bratton applauded political support for the police from the mayor, who provided funding for investments in officer hiring, training, equipment and overdose-reversal drugs.
One of the results is that police officers are using deadly force less often. As of Dec. 20, police officers intentionally fired their service guns in 23 encounters, a record low, down from 37 in 2016. The Police Department said officers were relying more on stun guns, which were used 491 times through November, compared with 474 times during the same period in 2016. More than 15,000 officers have been trained how to use them.
But criminologists differ about the cause of the continued declines. Mr. Zimring said that while better policing accounted for much of the decline in crime since 1990, it was no longer a primary driver. New York is “tiptoeing” toward a 90 percent crime decline for reasons that remain “utterly mysterious,” he said.
More broadly, research suggests that crime trends are closely tied to economic conditions. Interest rates, inflation and unemployment are among the macro-level factors influencing crime, according to James Austin, the president of the JFA Institute, a criminal justice policy nonprofit.
“What the Fed does will have more of an impact than any sentencing or police reforms,” Mr. Austin said.
The reductions in New York are a part of what the Brennan Center for Justice expects will be a 2.7-percent decline in crime rates and 5.6-percent drop in murder rates across the country’s largest cities. After record-high bloodshed last year, killings in Chicago have declined 15 percent.
Through August, rape was down in New York City 7 percent compared with last year, but a small increase in September was followed by spikes in October and November. The New York Times first published accusations against Mr. Weinstein on Oct. 5.
Reports of rapes that had occurred in a previous year, meanwhile, were up almost 12 percent through November. In response, the Police Department is adding investigators to its Special Victims Unit and hasmodernized the techniques detectives use to investigate claims.
“We can’t answer definitively” what is driving the rise, Commissioner O’Neill told reporters at a crime briefing this month. “At least I can’t. But we’re seeing people coming forward and having faith in the N.Y.P.D. And that’s what we want to happen.”
Whatever the reason for New York’s crime reductions, the statistics do not capture the complete picture of public safety. Some crimes are not represented fully or at all: acts of domestic violence, sexual assaults, identity thefts, hate crimes, and shootings that don’t result in injuries or damage.
In some cases, the data annotates horrible crimes: an ISIS-inspired truck rampage on a Manhattan bike lane on Halloween that left eight people dead; the ambush killing of a police officer, Miosotis Familia, 48, who was shot in the head on July 4 while sitting in her R.V.-style command post in the Bronx; the death of Timothy Caughman, 66, a black man, at the hands of a sword-wielding white supremacist on March 20.
Increasingly, officers are receiving calls to help people in emotional crises. The police responded to 157,000 such calls in 2016. But only 7,000 officers have received crisis intervention training for handling those situations.
While most police encounters are resolved without officers resorting to deadly force, fatal police shootings of people in emotional distress — including Dwayne Jeune on July 31 in Brooklyn and Miguel Richards on Sept. 6 in the Bronx — have drawn scrutiny. A police sergeant, Hugh Barry, was indicted on murder charges in May for the fatal on-duty shooting of a mentally ill woman, Deborah Danner, in October 2016. His trial is scheduled to begin in January.”
