While U.S. Attorney General Jeff Sessions claims that Obama-era "soft" drug sentences led to a nationwide rise in violent crime, a new report from the Justice Department inspector general says those changes were unevenly applied and shouldn't be used to extrapolate national trends.

The report, released today, examines the impact of former Attorney General Eric Holder's 2013 "smart on crime" initiative, which ordered federal prosecutors to focus on the most serious crimes and to avoid charging certain low-level drug offenders with crimes that carried mandatory minimum sentences.

The inspector general found that, while Holder's directives appeared to result in significant changes in federal prosecutors' charging practices, the policy was unevenly applied. Large decreases in the number of drug convictions occurred in the Southwest, while the number of federal drug convictions actually grew in some regions, including Alaska, Hawaii, and much of the West.

"As a result, we determined that national trends should not be interpreted in such a way as to conclude that Smart on Crime had a uniform impact across all the nation's districts," the report concluded.

Yet that's exactly what Sessions attempts to argue in a Sunday op-ed in The Washington Post defending his decision to scrap Holder's policy.

"Before that policy change, the violent crime rate in the United States had fallen steadily for two decades, reaching half of what it was in 1991," Sessions writes. "Within one year after the Justice Department softened its approach to drug offenders, the trend of decreasing violent crime reversed. In 2015, the United States suffered the largest single-year increase in the overall violent crime rate since 1991."

Figuring out the impact of Holder's 2013 memo is a tricky business because of poor data on prosecutors and what sentences they seek, but the inspector general determined that the rate of federal drug offenders sentenced without a mandatory minimum rose from 40 percent in 2012 to 54 percent in 2015. That's a big change within the federal prison system—but of the estimated 2.2 million people incarcerated in the U.S., 86 percent of them are in state correctional systems. And when one digs into which federal defendants actually met the requirements under Holder's policy, it turns out those changes may have resulted in shorter sentences for only around 500 federal drug offenders each year.

Trying to tie a policy that resulted in just 500 lighter sentences annually to a national increase in violent crime is simply nonsensical, as my colleague Jacob Sullum explained earlier today:

Even if we assume that every drug offender who got relief under Holder's policy was a violent predator in disguise, there were not enough of them, and they would not have been free soon enough, to have any noticeable impact on the crime rate. Perhaps Sessions means that other criminals, taking note of the fact that some federal drug offenders who previously might have gotten five years in prison were now getting two or three years instead, were emboldened to commit violent crimes. That scenario is, if anything, less plausible.

There's plenty more to unpack in that op-ed. Former Reasonista Radley Balko also wrote a thorough fisking of Sessions, digging into his questionable use of statistics.