At first glance, the number seems like an error — as if an FBI statistician had accidentally transposed some digits in the bureau’s annual report on crime released earlier this week.

Were there really 765 murders in Chicago in 2016? A year after the city tallied 478, and the year before that 411? A reader unfamiliar with Chicago’s recent crime history would likely say the true number has to be 576 or, worst case, 675.

Alas, anyone who has been paying attention to violence in Chicago knows the FBI didn’t make a mistake — the shocking number is accurate. Chicago’s annual murder total jumped 86 percent in the space of two years, evoking memories of the early 1990s crack wars when annual homicide totals regularly approached 1,000.

As Fordham University law professor John Pfaff noted on Twitter, Chicago alone was responsible for 22 percent of the nationwide murder increase in 2016.

Although that horrifying statistic stands out, Chicago’s wave of killing wasn’t an aberration, nationally speaking. Six other major U.S. cities experienced a surge in murders in at least one year between 2014 and 2016. (RELATED: The FBI Just Confirmed What Sessions Has Been Saying About Violent Crime)

Baltimore, for example, recorded 211 murders in 2014, a relatively peaceful year for the violence-plagued city. The next year, homicides exploded by more than 60 percent to 344.

Chicago and Baltimore have something in common beyond seemingly intractable gang violence. Along with several other cities — St. Louis, Dallas, Charlotte, and Milwaukee — they were the site of significant civil unrest that erupted following the killing of black men by police officers.

In Baltimore, protests devolved into multi-day riots after Freddie Gray, a 25-year-old drug dealer, died from injuries suffered while being transported in a police van in 2015. Similar riots occurred in Milwaukee and Charlotte after the fatal shootings of black men by police officers in 2016.

Though it did not experience riots, Chicago was the scene of significant anti-police protests after city officials released video footage of a police officer shooting and killing 17-year-old Laquan McDonald.

Some criminal justice experts say there is a causal link between the unrest and the two-year rise in homicides nationwide. Heather MacDonald, a fellow at the Manhattan Institute, has dubbed the phenomenon the “Ferguson Effect,” in reference to a rise in violent crime that followed shooting of Michael Brown by Ferguson, Mo., police officer Darren Wilson in 2014.

As McDonald sees it, agitation by groups such as Black Lives Matter, encouraged by slanted media coverage, has led to a retrenchment among big-city police forces. Street cops are so worried about being vilified by city leaders and the press that they are avoiding contact with the criminal element, she says.

“Cops are backing off of proactive policing in high-crime minority neighborhoods, and criminals are becoming emboldened,” MacDonald wrote in a Sept. 25 piece for City Journal. “Having been told incessantly by politicians, the media, and Black Lives Matter activists that they are bigoted for getting out of their cars and questioning someone loitering on a known drug corner at 2 AM, many officers are instead just driving by.”

Critics have said MacDonald’s theory is not supported by statistical evidence, noting that big spikes in violence occurred in just a handful of cities. If the Ferguson Effect were a real phenomenon, they argue, it would have manifested itself across the country.

“It’s really a local problem, not a broad trend,” Ames Grawert, an attorney with the Brennan Center for Justice, told The Intercept in 2016. “There is no evidence that crime has gone up overall.”

Another year’s worth of FBI data, however, adds weight to MacDonald’s argument. Killings have spiked in several cities that experienced rioting or significant protest against the police.

Dallas, for example, recorded 171 murders in 2016 — 47 percent more than in 2014. The story was the same in Charlotte and Milwaukee, whose 2016 homicide totals were 43 and 57 percent higher than in 2014, respectively.

Nowhere is the correlation between reduced police activity — what MacDonald calls “de-policing” — and a higher number of murders stronger than it is Chicago.

Earlier this year, the University of Chicago issued a report on the data behind the city’s horrifying rise in gun violence in 2016. After concluding the wave of murders couldn’t be attributed to warm weather or a decrease in educational or social welfare spending, the report suggested a precipitous drop in police stops might be a causal factor.

Police stops tumbled by more than 80 percent from November 2015 to January 2016, according to the report. The three month decline in police activity coincided with an intense period of scrutiny on the Chicago Police Department after it released video footage of the Laquan McDonald shooting. The video sparked a wave of protest in Chicago and a Department of Justice (DOJ) investigation of the police department.

While the U of C report said the connection between the McDonald incident and reduced police activity was “unclear,” it did note that the decline in police stops “began a few months before rates of gun violence in Chicago began to increase.”

As in Chicago, Baltimore’s spike in murders immediately followed a nationally scrutinized police-involved killing.

Peter Moskos, a former Baltimore cop turned professor at the John Jay College of Criminal Justice, has charted the city’s combined average of shootings and homicides per day in the periods preceding and following April 27, 2015, the day of the riots. He notes a spike in violence immediately after the unrest and the decision by state’s attorney Marilyn Mosby to bring “flimsy” charges against the six police officers involved in Gray’s arrest and transport.

Moskos says the surge in violence was an especially harmful example of the “Ferguson Effect.” City leaders and the DOJ instructed Baltimore police to be less proactive because aggressive discretionary policing of low-level offenses disproportionately affected minorities. This had a devastating, but predictable, effect on violent crime, Moskos wrote in a blog post earlier this month:

Murders and shooting increased literally overnight, and dramatically so. Of course this took the police-are-the-problem crowd by surprise. By their calculations, police doing less, particularly in black neighborhoods, would result in less harm to blacks. And indeed, arrests went way down. So did stops. So did complaints against policing. Even police-involved shootings are down. Everything is down! Shame about the murders and robberies, though.

Even if “de-policing” offers only a partial explanation for the explosion of killings in Chicago and Baltimore, it is now clear that both cities are suffering through a sustained period of violence, not a one-year anomaly.

In 2017, the number of murders in Chicago has fallen off but remains well above pre-2016 levels. The city had 519 murders through September, according to DNAinfo Chicago, putting it on pace to reach just shy of 700 for the year.

The problem is worse in Baltimore, where the number of homicides has barely budged from its post-Freddie Gray peak. After after a slight dip in 2016 when the city recorded 318 murders, Baltimore is on track to hit about 350 this year.

To put Baltimore’s murder epidemic in perspective, New York, which has more than 13 times as many residents, is expected to have about 300 murders in 2017.

The stark contrast suggests that, at least in some cities, the phenomenon described by MacDonald and Moskos is no myth.

WATCH VIDEO OF VIOLENCE ERUPTING DURING UNREST IN FERGUSON:

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