Donald Trump calls it a “crime wave” and “killing wave.” The New York Times calls it a “startling rise in murders” in “cities across the nation.” But “it” seems based on anecdotes and ideological claims–particularly among those arguing that protests against police misconduct have demoralized cops and/or “emboldened” killers.

So FiveThirtyEight undertook a quick project to discern what’s actually going on with homicide rates in the larger American cities, and quickly found out the data we usually rely on for information on crime rates, compiled by the FBI, simply isn’t available yet for the current year. They also discovered individual cities have wildly different methods of calculating and even classifying recent crimes. Having stipulated all that, FiveThirtyEight folk did their best to compare 2015-2016 YTD homicide rates for 59 cities (they aimed at 60, but Anaheim did not cooperate), and reached these conclusions, as written up by Carl Bialik:

[I]n 25 [cities], homicides were up by 20 percent or more from a year ago. Overall, homicides were up by 16 percent.1 But the picture varies a lot by city: Homicides are up 76 percent in Milwaukee, but down 43 percent in Boston. They’re also down in 19 other cities….

While a 16 percent increase in U.S. major-city homicides is statistically significant, it comes after decades of declines — the murder rate fell by more than half nationally from its peak in 1980 to 2012.

And big annual fluctuations aren’t unusual. For instance, in 2009, 17 of today’s 60 most populous cities had statistically significant decreases in the number of homicides, while just four had increases. In 1998, those numbers were 20 and four, respectively. Just a decade ago, in 2005, there were 15 cities with significant increases, roughly as many as this year. In 1986, 28 cities had significant increases; just two had decreases.

To the extent that some cities have definitely seen a significant increase in murders, the contributing factors are extremely murky:

[Milwaukee Police Chief Edward] Flynn and other police chiefs met in Washington, D.C., last month to discuss the crime spike some were seeing in their cities. They identified potential factors that could account for the concurrent increase in distant cities, such as the growth of the heroin trade and of criminals’ use of automatic weapons; inadequate services for offenders to return to civilian life when they are released from prison; and a decrease in federal funding for local policing.

And they discussed the difficulty chiefs face in getting data from one another’s cities.

You will notice the chiefs made no mention of #BlackLivesMatter or “illegal immigrant gangs” or police demoralization as potential factors.

The bottom line is that it’s extremely premature to make any judgments about a change in the long-term national decline in violent crime (including homicides), and crazy premature to be assigning causes for a “national crime wave” that may not even exist. Yes, there’s clearly something going on in Baltimore, Milwaukee and St. Louis, and liberals should be no means ignore or rationalize it. But glibly assuming we know what’s behind it is an act of gross irresponsibility. Then again, nobody’s called the pols and pundits yelling about a crime wave “responsible.”

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Ed Kilgore is a political columnist for New York and managing editor at the Democratic Strategist website. He was a contributing writer at the Washington Monthly from January 2012 until November 2015, and was the principal contributor to the Political Animal blog.