"Homicides last year increased by 17 percent in America’s 50 largest cities. That’s the largest increase in 25 years."

Donald Trump on Thursday, July 21st, 2016 in his acceptance speech at the Republican Natiional Convention in Cleveland

Donald Trump says homicides are up 17 percent in 50 biggest cities, largest increase in 25 years

Donald Trump accepted the Republican nomination with a speech full of concern about a breakdown in law and order.

"Decades of progress made in bringing down crime are now being reversed by this Administration’s rollback of criminal enforcement," he said. "Homicides last year increased by 17 percent in America’s 50 largest cities. That’s the largest increase in 25 years."

We’ll give Trump credit for sticking close to what we presume is his source material. We located an almost identical passage in an article published in January 2016 by the Wonkblog team at the Washington Post: "The number of homicides in the country's 50 largest cities rose nearly 17 percent last year, the greatest increase in lethal violence in a quarter century," the article began. The article cited Wonkblog’s own calculations.

However, Trump ignored some significant cautionary notes in that same story. The Post article said that a close look at the figures "suggests no single explanation for the increases and reveals no clear pattern among those cities that experienced the most horrific violence."

For instance, the article noted that other data shows a more modest increase. "A preliminary FBI report released last week showed that the overall number of violent offenses increased just 1.7 percent nationally during the first half of the year while the number of property crimes declined 4.2 percent," the Post article noted.

The article also noted that the increases are scattershot.

"There were more killings in Nashville, but the total in Memphis declined by 1 percent," the Post article noted. "The number of homicides increased 25 percent in Houston, but decreased 9 percent in San Antonio. There were seven fewer homicides last year than in 2014 in Fresno, Calif., a decline of 15 percent. Meanwhile, up Highway 99 in Sacramento, there were 43 killings last year, an increase of 54 percent."

"There's no national pattern," Franklin Zimring, a criminologist at the University of California at Berkeley, told the Post.

Darrel Stephens, executive director of the Major Cities Chiefs Association, agreed. "Everything is basically anecdotal," he told the Post. "There's not a clear national picture that I've been able to discern of what might be contributing to the changes."

James Alan Fox, the interim director of the School of Criminology and Criminal Justice at Northeastern University, told PolitiFact that the most recent data is heavily driven by four large cities with disproportionate increases -- Chicago, Houston, Washington and Baltimore.

Fox and others urged PolitiFact not to make too much of changes in data over the course of a single year. It’s better to look at a range of years to spot lasting trends.

"There is volatility in numbers like these," he said.

For instance, he said, in 2012, there were more than 500 homicides in Chicago. That fell to the lower 400s each of the next two years before rising again to the high 400s in 2015.

"Ironically, some of the time when the numbers go up it may be because there was an unusually low number the previous year. A one-year change is not a reliable trend," Fox said.

And over the long term, rates of violent crime have moved in the right direction. As we have previously noted, FBI data shows that violent crime has been falling on an almost uninterrupted basis since the early 1990s. The data below shows violent crime per 100,000 population from 1993 to 2014, the last full year for which data is available.

"Homicide rates have declined steadily since 1993, through both Republican and Democratic presidencies," said Raymond Paternoster, a University of Maryland criminologist.

And as a result of this long-term decline, the crime rate has been "low for so long that a tiny increase becomes a large percent increase," said Alan Lizotte, criminal justice professor at the University at Albany.

Our ruling

Trump said, "Homicides last year increased by 17 percent in America’s 50 largest cities. That’s the largest increase in 25 years."

The statement comes from a credible source -- calculations made by the Washington Post. However, in painting a bleak picture, Trump cherry-picks the Post’s overall findings -- and makes mistakes criminologists warn about.

The Post article acknowledged that FBI data found a smaller increase in recent years, with contradictory results for many cities. And experts caution against putting too much stock in short-term changes, since year-to-year data can be volatile for hard-to-discern reasons.

Lost in Trump’s formulation is that, overall, violent crime has been falling consistently for about a quarter century. The statement contains an element of truth but ignores facts that would give a different impression, so we rate his claim Half True.