Readers of USA Today opened their newspapers on Tuesday to find an op-ed by Attorney General Jeff Sessions celebrating a decline in the nation’s crime rates. The attorney general took credit for the drop on behalf of the Trump administration, arguing that his department’s policies since taking office last January had reversed a two-year increase in violent crime and thefts.

“When President Trump was inaugurated, he made the American people a promise: ‘This American carnage stops right here and stops right now,’” Sessions wrote. “It is a promise that he has kept.”

But those claims aren’t supported by the evidence Sessions provided, experts said. It’s the second high-profile episode this month in which the Justice Department has made misleading claims with statistics. Last week, a joint DOJ and Department of Homeland Security report used flawed evidence to link immigration to terrorist attacks committed inside the United States. The Daily Beast reported after its release that Sessions’s office largely crafted that report, cutting out career Homeland Security analysts in the process.

In Tuesday’s op-ed, Sessions laid out a three-act history of crime in modern America. The first act stretches from 1961 to 1985, when the nation saw a steady rise in murders and other major crimes. Then came the second act, when he and other federal officials in that era struck back. (Sessions served as a federal prosecutor in the 1980s and 1990s before his election to the Senate in 1996.) “We went to work, and the results were transformational,” he wrote. “Crime in America began to decline.” Indeed, violent crime was cut in half by 2014 from its height in 1991.

His third act takes place over just two years: 2015 and 2016, when violent crime once again began to surge. “The violent crime rate went up by nearly 7 percent,” Sessions wrote. “The robbery rate went up. The assault rate went up nearly 10 percent. The rate of rape went up 11 percent. And the murder rate went up by a shocking 20 percent.” The attorney general does not explain why this happened. What matters is how it was solved: by the election of President Donald Trump and by the policies Sessions enacted as his attorney general.

“Trump ran for office on a message of law and order, and he won,” Sessions wrote. “When he took office, he ordered the Department of Justice to stop and reverse these trends—and that is what we have been doing every day for the past year.”

Sessions gets the broad contours right. Violent crime rose throughout the 1970s and 1980s until it peaked in the mid-1990s, after which it steadily and dramatically fell in the Great American Crime Decline. He’s also correct that the rates ticked upward again in 2015 and 2016, which marked the first two-year rise since the Great Decline began. And he’s right that the FBI’s preliminary data from the first half of 2017 shows a drop once again in overall violent crime, although homicides continued to rise.

But experts are skeptical that Sessions’s Justice Department played a role in that change. “There is no way that policy that was implemented in the last few months could have caused a nationwide reversal in crime trends, as they claim,” Inimai Chettiar, the director of the Brennan Center’s Justice Program, said.

Further research, she added, will be needed to determine what happened in 2015 and 2016, as well as why it went down again in 2017. Trump and Sessions spent the last few years claiming that those two years heralded a new crime wave—one that only they could hold at bay. But one or two years of higher rates doesn’t necessarily mean a return to the bad old days. “Crime doesn’t just steadily decrease year by year,” Chettiar explained. “Sometimes it goes up and comes back down. You would never expect it to just continue going down.”

John Pfaff, a Fordham University law professor who studies crime and prison statistics, says that Sessions is overstating the federal government’s role in the equation. “Federal officials want to feel like the decisions they’re making are playing a big role in fighting crime,” he explained. “The fact is, their overall impact is generally not that large.”

Take, for instance, Sessions’s claim that a change in policies at the Justice Department played a role. In the first few months of his tenure, the new attorney general reversed Obama-era guidelines aimed at curbing mass incarceration and instructed federal prosecutors to seek the maximum possible sentences for low-level drug crimes instead. Sessions also scaled back the use of federal consent decrees to reform troubled police departments. “We have placed trust in our prosecutors again, and we’re restoring respect for law enforcement,” he wrote on Tuesday.

But local and state prosecutors, who handle the overwhelming majority of criminal cases in the United States, weren’t affected by the change. “Whatever impact the criminal justice system has on crime, it’s the state and local officials who have an impact, not the federal officials,” Pfaff explained. “[Sessions] says at one point that they’ve convicted ‘nearly 500 human traffickers and 1,200 gang members.’ The states convict nearly a million people a year. So he’s just listed 0.1 percent at best of all convictions.”

Criminal justice reform rose to prominence within Democratic and Republican policy circles in recent years, but Sessions has kept the tough-on-crime faith. Chettiar, whose organization has advocated for federal and state reforms, said the attorney general’s approach isn’t supported by research. “What studies have found, including our own, is that local policing and socioeconomic factors affect crime the most and that the draconian policies they’re trying to implement and have been implementing do very little to bring down crime,” she explained.

Any explanations for why crime rises and falls in a specific time span should be made with humility. The Great Decline was one of the most profound social shifts in the last 25 years of American life, but scholars still haven’t reached a consensus on what caused it. A 2015 Brennan Center survey of the available research concluded that multiple factors played a role. Of those factors, the report estimated that increased policing accounted for part of the drop but not most of it.

“We still don’t have a good understanding of what caused crime to fall,” Pfaff said. “And it’s increasingly clear that the formal criminal justice system was only some small part of that, or at least it was only a part of that and not the sole factor.” He also pointed out that the system’s effects on crime came with immense consequences in the form of mass incarceration, which has had far-reaching effects on American life.

Ironically, the scale of the Great Decline makes it easier for Trump and Sessions to claim a crime wave had taken place in 2015 and 2016. “When crime is low, any given absolute change will be a bigger percent change,” Pfaff explained. “If you had 1,000 more murders when there were 10,000 murders the previous year, then that’s a 10 percent jump. If you have 1,000 more murders when there was only 2,000 murders before, that’s a 50 percent jump.”

There’s no such thing as a good increase in crime rates. But the double-digit percentage jumps that Sessions listed in his op-ed don’t give a complete picture of crime’s long-term trends. “They can say this is the largest percent change in years, and they’re right, but that’s because we’ve done such a good job of getting crime down that any absolute increase is going to look worse in percentage terms,” Pfaff said.

Another key difference between now and the high-crime era of a quarter-century ago is a stark geographic disparity of local crime. “You saw a broad increase in homicides across major cities in the late 1980s and early 1990s,” Pfaff said. “Here, it’s been driven by a much smaller number of cities.” When murders jumped in 2016, for example, he pointed out that 22 percent of that increase in homicides that year could be attributed to Chicago. In fact, 10 percent of the national rise in murders could be traced to just five neighborhoods in that city.

That extreme localization suggests that regional factors may be more important than national ones right now. If so, it also undercuts Sessions’s boasts that his harsher federal policies have produced a national reduction in crime, as well as his predictions that he can keep it lower in the years to come.