The NYU School of Law’s Brennan Center for Justice, in its annual report on crime, finds that the murder rate in America’s 30 largest cities rose 13.1 percent in 2016—an alarming figure, especially considering last year’s identical increase. Striking a calming note, the Brennan Center’s press release accompanying the report begins by reminding us that “Americans are safer today than they have been at almost any time in the past 25 years.” But downplaying the recent uptick in the homicide rate distracts from the fact that there is more than one America when it comes to violent crime: indeed, 51 percent of all U.S. murders are committed in just 2 percent of the nation’s counties, according to the Crime Prevention Research Center.

No city more starkly illustrates this disparity than Chicago. Many scoffed at President Trump’s tweets about federal help to stop the “carnage” there. “Chicago’s murder rate wasn’t even in the top 10 among large cities,” tweeted USA Today law and justice reporter Brad Heath in response. The Atlantic observed that “there are a number of cities . . . that have much, much higher homicide rates.” A CNN column argued that “a deeper dive into the numbers shows fears over the city’s violence can be overblown when compared to cities much smaller.”

But Chicago—which, the Brennan Center concedes, “accounted for 55.1 percent of the total increase in urban murders” in 2016—deserves its reputation as an American murder capital, or at least a significant part of it does. If policymakers, journalists, and others really wanted to take the “deeper dive” into the numbers that CNN suggests, they should try looking at neighborhood crime statistics. Doing so reveals that, within Chicago, a large sub-city exists that is, in fact, the most dangerous big city in the United States.

It’s true that Chicago, with a citywide homicide rate of 27.9 per 100,000 people, has relatively fewer murders than seven other large cities, including St. Louis, Baltimore, Memphis, and Detroit. Much of Chicago sees few murders. A better way to understand Chicago homicides is to break them down by police district. To see how concentrated the city’s murders are, I isolated the precincts in which approximately 75 percent of the homicides occur and compared that area—call it Sub-Chicago—with the U.S. cities that are supposedly more dangerous than the Windy City.

During the 365-day period beginning June 7, 2016, Chicago had 711 first- and second-degree homicides. Of those, 556 (or 78.1 percent) occurred in just ten of the city’s police districts. Those districts—which are contiguous—constitute a geographical area almost half the city’s size and house 40.3 percent of the city’s nearly 2.7 million residents. With a population of almost 1.1 million, Sub-Chicago would itself be one of America’s largest cities, and, with a homicide rate of 51.2—almost double Chicago’s 2016 citywide rate—it would be in the running for the title of America’s most dangerous, as it is just shy of surpassing the 2016 citywide rates of Baltimore and St. Louis. Nowhere else in the country is there an area so large and so heavily populated with a murder rate this high.

Even when you look at the areas of concentrated homicide in other cities—i.e., those that encompass close to 75 percent of a city’s murders—Sub-Chicago stands out. In St. Louis, for example, 184 murders were committed during the period beginning May 1, 2016, and ending April 30, 2017. Of those, 136 (or 73.9 percent) occurred in three of the city’s six police districts (Sub-St. Louis). Those three districts cover 50.6 percent of the city’s 63.8 square miles, which, according to the city website, house 135,920 (or 42.5 percent) of the city’s 319,294 residents. A similar tract of Sub-Chicago, made up of police districts 11 and 15, with 140 murders and a population of 129,932, posted an annual murder rate of 107.7 per 100,000 during the 365-day period studied—slightly higher than the area constituting Sub-St. Louis (100.05).

In Memphis, murders in 2016 were more evenly distributed than in Chicago and St. Louis. Last year, 76.3 percent of the city’s 228 murders occurred in six of the city’s nine police districts, which cover about 80 percent of the city’s land area and house 76 percent of its population. The murder rate of those six districts was 34.8 per 100,000—less than three points higher than the citywide rate and almost 20 points lower than that of Sub-Chicago.

Analyses of Detroit and Baltimore yield similar results. In Detroit, 72.8 percent of the city’s 302 murders in 2016 occurred in seven of the city’s 11 police precincts—an area that constitutes 64.1 percent of the city’s 137 square miles and accounts for almost 70 percent of its 672,972 residents. Sub-Detroit’s 2016 homicide rate was 47.1 per 100,000 residents—significantly lower than Sub-Chicago’s and less than three points higher than Detroit’s citywide rate.

Seventy-six percent (242) of Baltimore’s murders occurred in six of the city’s nine precincts—an area that houses 53.1 percent of the city’s 624,271 residents. That area’s murder rate is a scary 72.9 per 100,000 residents. But Sub-Chicago has almost double the population of Sub-Baltimore. Sub-Chicago’s four most dangerous police districts—the 11th, 7th, 15th, and 16th—experienced 273 murders during the period analyzed. With a population of 291,844, it posted a murder rate of 93.5—more than 20 points higher than that of Sub-Baltimore.

­­­­­­What this analysis shows is that, in many American cities, a substantial number of residents live through what can only be described as a homicide epidemic. And, despite assurances to the contrary, nowhere is that epidemic more pronounced than in Sub-Chicago, which happens to be 88 percent black and Latino. If we’re serious about improving life in places like South and West Chicago, we must confront the uncomfortable truths about crime concentration in U.S. cities. Step one is recognizing that while most of the country is relatively free from such violence, a portion of the country lives in the urban equivalent of a killing field. These Americans don’t need to be told that crime is down nationwide; they need protection.

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