Inside the Meter

Guest column: Fact-check on increase of mass shootings shows difficulty of parsing statistics

Editor's note: David Jolly is PolitiFact's Republican guest columnist and a former member of the U.S. House of Representatives serving Florida's 13th congressional district from 2014-17. Read more about the guest columnist position here.

In his first critique, Jolly is writing about a fact-check of a claim about an assault weapons ban made by Democratic Rep. Ted Deutch, which you can read here. His post has been edited only for style and grammar.

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Statistics are one of the clearest ways for politicians, fact-checkers and impassioned voters to make a salient point. We rely on statistics to convey effectiveness of public policy, clarity of public opinion, and emerging trends and priorities of the body politic. The use of statistics, however, also creates an almost certain opening for statements to be studied, evaluated and challenged.

PolitiFact’s Feb. 23 fact-check studying a U.S. congressman’s statement regarding the increase in mass shootings since the expiration of the assault weapons ban provides one of the clearest examples of both the simplicity and the challenge of using, and evaluating, statistics.

At a recent CNN town hall regarding the shooting at Parkland and the ensuing national debate over firearms, Rep. Ted Deutch stated, "Let’s be clear, mass shootings went up 200% in the decade after the assault weapons ban expired."

Rep. Deutch is said to have relied on statistics provided by The Century Foundation, a left-leaning think tank, which plainly assessed there had been "an increase of over 200%" in mass shootings since the expiration of the assault weapons ban. PolitiFact, however, rated Deutch’s statement Mostly False, largely on the basis that the commentary upon which the congressman relied was substantively challenged by other experts in the field. Presumably, had Deutch said in the town hall, "According to The Century Foundation, mass shootings went up 200% in the decade after the assault weapons ban expired," PolitiFact would have found the Congressman’s statement True on its face, while ruling the findings of The Century Foundation Mostly False.

Moreover, had PolitiFact evaluated Deutch’s statement simply on the numbers, there is ample evidence in the PolitiFact article to support a ruling of Mostly True. In fact, in its own evaluation PolitiFact cites a second analysis that found a 183 percent increase in mass shootings since the ban expired, and PolitiFact acknowledges "mass public shootings have become deadlier over the last decade, as the number of victims shot and killed has increased since the expiration of the assault weapons ban." PolitiFact rightly asserts in its evaluation, however, that leading experts caution these numbers do not adequately adjust for population growth since the ban’s expiration, nor do they prove cause and effect — that the expiration of the ban is the reason for the spike in mass shootings.

Which leads to a final challenge for fact-checkers. PolitiFact seems to presume that Congressman Deutch was, in fact, asserting a specific cause and effect, and PolitiFact appears to have made its ruling in part on that presumption. It is not an unfair approach, but it does create a baseline subjectivity in evaluating Deutch’s assertion. Whether Deutch was indeed making a cause and effect argument or was merely suggesting there is a trend that merits studying the impact of the expiration of the assault weapons ban is not readily apparent within the four corners of his statement.

In this case, a congressman’s statement seems to have been ruled Mostly False on two primary factors — his citing a credible think tank’s commentary on gun violence statistics, and a drawn inference by fact-checkers that may or may not have been intended in the congressman’s statement. Neither makes PolitiFact’s ruling right or wrong, but it reflects the enormous challenge faced by politicians, fact-checkers and ultimately voters in today’s political environment.