OVER the past two years America has become more murderous. After steadily falling for a quarter-century, the national homicide rate jumped by 11% in 2015. Last year, an escalation of gang violence in Chicago increased the number of killings there from 485 to 764. Donald Trump, America’s president, has threatened to “send in the feds” if Chicago doesn’t “fix the horrible carnage”. But whether the crime increase in the Windy City is merely an isolated event or reflects a wider trend remains unclear.

To help resolve this debate, The Economist has gathered murder statistics for 2016—fully eight months before they are released by the FBI—for 50 of America’s most violent cities. These areas contain 15% of the country’s population and around 36% of its murder victims. Our numbers show that homicides rose in 35 of them. Since urban trends tend to track national ones, this suggests that the overall murder rate is indeed rising at its fastest pace since the early 1970s. However, today’s violence still needs to be set in historical context. Across all 50 cities, the homicide rate was lower in 2016 than it was in 2007, and for the 26 years before that.

The interactive chart above shows that the 50 cities fall into four categories. In each group the level and trajectory of murder rates differ: they are low and stable in 13 cities (among them New York and Los Angeles); in 15 they are low but increasing (Houston and Las Vegas); in 9 they are high but stable (Philadelphia and Detroit); and in 13 they are high and rising (Chicago and Indianapolis).

It is too early to know precisely what has caused this spike in violence. And factors that affect one city may not afflict another. Newark, just ten miles from New York City, has a murder rate nine times higher. And unlike New York, where homicides have fallen 85% from their peak in 1990, in Newark they have barely budged. Much of that difference can be explained by demography, deprivation and policing.

As our article in this week’s print issue discusses, digging into the data offers a few clues about what might be happening at the national level. Crunching numbers on 280,000 murder records from 1980 to 2015 shows that among our 50 cities gun use has increased from 65% to 80% of all murders. But that number varies dramatically by city. Guns were responsible for 60% of murders in New York and 85% in Chicago between 2010 and 2015. Although both places have made progress in reducing non-gun-related homicides, Chicago’s gun murder rate is five times New York’s. With luck, when country-wide data are released, they will show that the rest of America is much more like the Big Apple than the Windy City when it comes to violent crime.