Offering a hint of hope to a city notorious worldwide for its gun violence, Chicago saw a decline of more than 100 homicide victims in 2017 compared with the previous year — the steepest one-year reduction in nearly 15 years.

But Mayor Rahm Emanuel’s administration, a beleaguered police department and residents of the blighted neighborhoods where the bloodshed is largely concentrated nevertheless are faced with a horrific toll: 664 people slain within city limits by New Year’s Eve, plus seven people shot dead by on-duty Chicago Police officers, according to data compiled by the Chicago Sun-Times.

Still, the 15 percent decline in killings compared with 2016 is stark, especially given a grisly first half of the year when the city was on pace to surpass the 781 homicides logged last year — Chicago’s deadliest in two decades.

Police and criminologists will be waiting to see if that improvement, bolstered by new crime-fighting technology and renewed outreach efforts by a police department laboring to restore community trust, can be sustained — or if it simply was a temporary lull during a terrifying spike of more than 1,400 people slain in two calendar years.

“When we look at month-by-month homicide counts in Chicago, we see that the numbers for 2017 really start to diverge from 2016 starting around August, and then there seems to be a persistent gap through most of the rest of the year,” said Jens Ludwig, director of the University of Chicago Crime Lab, which has teamed with the CPD to evaluate crime-reduction strategies.

“What is unclear is whether that divergence is the start of a trend, or just a temporary blip in the data, so we’ll want to be watching these monthly year-over-year numbers very closely as we go into 2018,” Ludwig said.

Chicago Police Supt. Eddie Johnson said the 2017 dip gave the city “room for encouragement.”

“We should be encouraged by what we’re seeing, because we easily could have gone the other way,” Johnson told the Sun-Times in a year-end interview.

More than 3,500 people were shot in Chicago in 2017, Sun-Times data show, but the number of shooting incidents dipped by more than 21 percent, a decline of about 800 gunshot victims compared with 2016, according to police.

Chicago Police Supt. Eddie Johnson | James Foster/Sun-Times file photo

“We all know 2016 was a horrible year. Now you’ve got more than 800 families who don’t have to suffer through the trauma of gun violence,” Johnson said.

He pointed to significant gains made in his department’s Englewood and Harrison districts, spanning Chicago’s two most violent crime-ridden areas on the South and West sides. Shootings fell by 26 percent in Harrison compared with 2016, and 43 percent in Englewood, which had the city’s biggest drop.

“I never thought I’d see that as a Chicago Police officer,” Johnson said.

He credited much of the improvement to new technology-driven policing strategies that were rolled out in those districts. Analysts from the U. of C. Crime Lab work alongside police in Strategic Decision Support Centers, using gunfire detection data and predictive software to suggest where officers should be deployed.

The support centers were expanded to four additional districts, seeing an average combined shooting reduction of about 25 percent, according to police, who are set to introduce the centers to six more districts in 2018.

“Those technologies have helped us get more proactive,” Johnson said. “If we can duplicate those reductions in 2018, that means in a two-year time frame, we will have a 30 percent reduction in murders, and a 40 percent reductions in shootings.”

Ludwig said Crime Lab data show the data-driven strategies “had a particularly pronounced impact” in Englewood, and are “at least partially responsible” for the citywide decline.

But Ludwig tempered the credit given to the CPD’s new nerve centers, saying it “seems unlikely to be the whole story behind the drop.” He noted that Milwaukee suffered a similar surge in gun violence from 2015 to 2016 as Chicago did, and was expected to see a similar decline in 2017 homicides.

Jens Ludwig, director of the University of Chicago Crime Lab, speaks at Harper High School in 2012. | Brian Jackson/Sun-Times file photo

“That suggests that the explanation for Chicago’s trend from 2016 to 2017 might come in part from some other things that are changing at least at a regional level, if not national level, rather than being due entirely to Chicago-specific factors,” Ludwig said.

The second part of the equation, Johnson said, was rebuilding trust with with city residents.

“We need to be more engaged with the communities we serve,” he said.

Chicago Police reported 650 murders through Dec. 30, a figure lower than the Sun-Times’ count because it does not include homicides on city expressways, which fall under the jurisdiction of Illinois State Police, or killings deemed justified by CPD investigators, as in cases of self defense. The Cook County medical examiner’s office reported 685 Chicago homicides through Dec. 30, which includes people killed by police, and those who died of wounds suffered in previous years.

Regardless of criteria, Chicago’s body count remains alarming, dwarfing those in larger cities like New York and Los Angeles, where 2017 homicide tallies stayed under 300 — a figure that Johnson said the city can reach.

“I think that’s a reasonable goal that we can get to. And at some point, I think that we will get there,” he said. “It’s going to take a joint effort between the police department, residents, clergy, business owners and elected officials.”

Most of the city’s slayings have gone unsolved, with detectives’ year-end clearance rate hovering at “roughly 40 percent,” CPD spokesman Anthony Guglielmi said. That’s still a marked uptick from four months ago, when analysts said the clearance rate fell below 20 percent.

Takiya Holmes, 11, Lavontay White, 2, and Kanari Gentry-Bowers, 12, were killed within a period of four days in Chicago. | Family photos

A review of the Sun-Times data show that the faces of homicide cases in 2017 resembled the bulk of those in years past: young men, typically people of color, gunned down in economically depressed areas on the South and West sides. Black or Hispanic men between 18 and 40 years old accounted for nearly two-thirds of the dead.

But the bloodshed spanned generations, touching all parts of the city.

Jenae Lemon was the youngest of the victims, just 4 days old, delivered prematurely in September after her mother, Charnella Lemon, was shot dead in a vacant lot on the Far South Side, along with 33-year-old Terrence Carter.

Cook County Associate Judge Raymond Myles | Cook County Circuit Court photo

A bullet pierced the little Jenae’s torso through her mother’s abdomen, authorities found. No arrests have been made.

The newborn was among 27 of Chicago’s homicide victims who were 15 or younger — including six infants.

During one horrifying spell in February, three young children were slain by gunfire within three days of each other. A toddler, 2-year-old Lavontay White, was shot dead in North Lawndale in an attack streamed on Facebook Live; an alleged drug dealer’s stray bullet struck 11-year-old Takiya Holmes in the temple as she sat in the back seat of her family’s minivan; and 12-year-old Kanari Gentry-Bowers was gunned down on the playground of her South Side elementary school.

Donald McNamara was the oldest victim at 86, shot dead by a family member in his Canaryville home in August, authorities said.

Cynthia Trevillion | Chicago Waldorf School Community photo

Also among the slain were Cook County Judge Raymond Myles, the victim of a botched robbery attempt outside his West Chesterfield home; and beloved teacher Cynthia Trevillion, caught in the crossfire of a gang shooting while walking to a Rogers Park restaurant, authorities said.

Blood spilled down the road from O’Hare Airport, with few details of Jermin Beganovic’s slaying released beyond the fatal head wound he suffered on a Sunday afternoon.

And on an East Ukrainian Village sidewalk, where 67-year-old Benjamin Soto Ramirez was beaten to death in an attack described as torture.

Blood poured in South Shore on March 30, when seven people — including a pregnant woman — were shot to death within 12 hours and eight city blocks of each other.

In Brighton Park, assault rifles were used in a mass shooting that left eight people wounded, two people dead, and some residents feeling like a city alderman slapped their family members in the face by saying he was thankful “that no innocent lives were lost.”

As many of the same communities continue to be racked by killings, the underlying issues driving gun violence persist, officials said. Johnson and Ludwig each pointed to a dearth of jobs, affordable housing, mental health treatment and education — issues that have sent large swathes of the African-American population fleeing Chicago.

The superintendent also pointed to the backlash against his police department in the wake of the Laquan McDonald shooting video release, a scandal that triggered the mayor’s axing of Johnson’s predecessor, a scathing Justice Department report and an ongoing image overhaul at police headquarters.

“You couple that with the national anti-police narrative, that set us up for a disastrous 2016, and we saw it,” Johnson said. “Don’t get me wrong, you have to look at those things to ensure that it doesn’t happen again. But I think a lot of criminals felt emboldened because of the national narrative. They didn’t feel like we were holding them accountable.”

Ludwig noted that a unique aspect of Chicago’s gun violence is its tendency to sweep in young people compared to other large cities. A quarter of homicide suspects in 2016 were between the ages of 10 and 19, Crime Lab researchers found, compared with 15 percent in other metro areas.

“It’s not just that there are social conditions in our most distressed neighborhoods that increase people’s risk of gun-violence involvement,” Ludwig said. “It’s that teenagers in particular seem to be particularly vulnerable to these factors.”