“I AM sick of President Trump denigrating Chicago,” said Bill de Blasio, the mayor of New York, during a trip to the Windy City on March 3rd, lamenting Mr Trump’s “particularly painful stereotyping” of the place. In January Mr Trump tweeted that he would “send in the Feds!” if the city did not fix the horrible “carnage” of gun violence. In his recent speech to a joint session of Congress, Mr Trump said it was not acceptable that more than 4,000 people were shot in Chicago last year.

With 764 murders in 2016, more people were killed in Chicago, America’s third-largest city, than in its biggest city, New York (334), and its second-biggest, Los Angeles (294), combined (see chart). Three children were killed in four days in February. Sending in the Feds, whatever it means, may sound appealing, but it would be unlikely to help. Though Mr Trump said that “very top police” in Chicago had told him that the city’s crime problem could be stopped in a week with tougher tactics, there is no single explanation for the rise in violent crime. Nor is there any quick fix. Many of the reasons frequently discussed, such as splintered gangs, an influx of guns from states surrounding Illinois, the demolition of public housing, concentrated poverty or even the weather, are things that have been around for years.

One thing is certain, says John Pfaff at Fordham University in New York: sending in the National Guard, as Mr Trump seemed to suggest, would send the wrong signal and would probably worsen the already sour relations between the police and black Chicagoans. Deploying troops—when local police are unable to contain unrest and the mayor of a city appeals to the governor, who oversees the state National Guard—should be a last resort.

Some things have changed, though. Gangs are using high-powered rifles that can tear through cars and even bulletproof vests. And the Chicago Police Department (CPD) made over 80% fewer street stops in January 2016 than it did in November 2015. The officers’ retreat was related to a public outcry after the release of video footage in November 2015 showing the execution-style killing of a black teenager by a white policeman. The furore resulted in the firing of the then-police chief, Garry McCarthy, as well as an investigation of CPD practices by the Department of Justice. A few months after that steep reduction in street stops, gun violence raced up.

This coincided with a sharp decline in the clearance rate for gun crimes in 2016. Last year 26% of murders resulted in an arrest, down from 36% in 2015, and arrests for shootings fell to 5% from 7%. Many assume the fall is related to black Chicagoans’ lack of trust in police officers, which in turn stems the flow of information needed to solve a crime. It meant that more than three-quarters of last year’s murderers walked free. That may have encouraged revenge killings, as the likelihood of getting caught was so low.

A long-running stand-off between the governor of Illinois, Bruce Rauner, and the state legislature, which has resulted in the disruption or end of many social programmes for Chicago’s poorest residents, is also a factor. Since March 2015 the funding of CeaseFire, which employs former felons and others with insight into local crime as community messengers to prevent violence, has been cut to almost nothing. The one district on the South Side where CeaseFire was not slashed was the only one that saw a drop in shootings. Spokesmen for the programme, known in other cities as “Cure Violence”, claim that if it were fully funded, murders in Chicago could be reduced to fewer than 350 a year; possibly even fewer than 200.

If that sounds self-serving, consider New York’s experience. After bolstering its police force, the Big Apple had success with community policing, which involves officers getting to know not just the criminals on their beat but also the business-owners, teachers and local families, in order to build trust. In Chicago, the vast majority of shootings and murders happen in four or five poor black or Latino neighbourhoods where unemployment is high, schools dreadful and urban blight omnipresent. In January almost half of the city’s 51 murders occurred in Englewood on the South Side and Harrison and Austin on the West Side. This lopsided number contains a hopeful sign: a concentrated problem is easier to tackle than one that is diffuse. Nor is Chicago fated to suffer: six days passed last week without a murder, the first time that has happened for four years.