A drop in homicides in Chicago alone accounted for a majority of the national decline in killings in 2017, recently released FBI statistics show.

The FBI reported a total of 17,284 murders across the U.S. in 2017, down from 17,413 total murders reported in 2016. That’s a net decrease of 129 murders across the country from 2016 to 2017. Eighty-six percent of that decrease can be attributed to Chicago specifically, which saw 112 fewer murders in 2017 compared to 2016.

A spike in killings in Chicago and a handful of other cities in 2015 and 2016 had interrupted a long, steady decline in the country’s murder rate.

Chicago saw 765 murders in 2016, the most in two decades. In 2017 that number dropped to 653 — a rate of about 24 murders for every 100,000 residents. That’s a drop in the city’s murder rate of 14.6 percent, outpacing the 1.5 percent drop nationwide.

Chicago’s drop in murders was reported earlier based on Chicago Sun-Times data. The FBI’s 2017 report on crime in the United States, which collects information from jurisdictions across the country based on a common set of standards, presents a chance to put the city’s position in a national context.

1Chicago’s murder rate is still higher than in any year since 1998. But the city could be on its way to an even more rapid fall in homicides in 2018, according to a report released Monday by the Brennan Center for Justice at New York University.

That report projected that Chicago’s homicide rate would fall by more than 23 percent in 2018, based on numbers reported so far this year and the typical month-to-month tempo of crime.

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Even given that decline, Chicago would still qualify as one of the country’s most crime-ridden cities.

“Even if 2018 comes in at a 25 percent reduction by the end of the year, that gets us back to roughly where we were in 2015, before the spike happened,” said Max Kapustin, the research director at the University of Chicago Crime Lab. “Which is a vast improvement, but still very far from a city like New York or Los Angeles, which is, I think, where Chicago ought to be.”

Among cities with over 100,000 residents, Chicago had the 14th highest murder rate, and the highest for cities with more than 1 million residents.

Some cities, such as Baltimore, have more than twice as many murders per person as Chicago. But others have dramatically lower homicide rates, like New York, which saw only three murders for every 100,000 city residents in 2017.

The FBI discourages evaluations of the safety of a city or the effectiveness of its police department on any one measure, including its murder rate.

Violent crime in Chicago also declined, according to the FBI report, with Chicago’s rate landing outside of the top 20 among cities with populations over 100,000. Chicago’s rate of violent crime declined by 0.6 percent, while the national rate of violent crime declined by 1.4 percent.

Violent crime also declined in the greater Chicago region, but increased slightly statewide.

The rate of murders solved by police nationwide increased from 59.4 percent in 2016 to 61.6 percent in 2017. Chicago’s “clearance rate” for murders, based on CPD data, has been falling for years, and hit a new low in 2017. Chicago, along with almost every other jurisdiction in Illinois, does not file its clearance rates with the FBI, according to a spokeswoman for the FBI Chicago field office, which makes it difficult to plot one-to-one comparisons with other cities or with national data.

As Chicago and the country recover from the last two years of grim patterns in crime rates, experts are facing pressure to determine what might have caused them. But some point out that, statistically speaking, an occasional leap in homicides isn’t that unusual.

“We saw crime and homicide rates pick up in 2003, 2004-ish, prompting very similar concerns, op-eds, detailed research analyzing what could be causing crime to increase, and grave predictions of the next crime wave around the corner,” said Ames Grawert, senior counsel in the Brennan Center’s Justice Program. “It didn’t happen then, and our theory was that it wouldn’t happen this time, either.”

Experts have looked for a link between high-profile police shootings and an uptick in crime overall, but Grawert said this has yet to be established.

It is also possible that new city-level policing strategies have made a difference.

For much of 2017, Grawert pointed out, Chicago was on track to match its record-setting 2016 murder rate, until there was a sudden drop in the incident rate during the last quarter of the year. Kapustin and Chicago Police Department spokesman Anthony Guglielmi both credited Strategic Decision Support Centers, collections of technology and analysts established in 2017 in six high-crime police districts with the help of Kapustin’s Crime Lab, with part of the late-2017 decline in crime.

“[The 2017 decline] is by no means a cause for celebration, but a call for further action and investment into the strategies and tactics that we know are working,” Guglielmi said.

As police departments in major cities across the U.S. experiment with new strategies to target violent crime, Kapustin says it’s essential for researchers to continue studying patterns in the data sure future fluctuations are more instructive.

“I think that its important to not have to be in the situation again where the uptick happens, and no one know why, and then the decline follows, and again, no one knows why,” Kapustin said.