A new report shows that sentencing disparities between similarly situated white and black offenders remain pronounced, providing evidence for concerns about systemic inequality in the federal criminal justice system.

The report, issued by the United States Sentencing Commission (USSC), compares sentences for similarly situated offenders sentenced between October of 2011 and September of 2016. It is the fifth such report the USSC has issued since 2003.

The report found that black male offenders' sentences were 19.1 percent longer than those of similarly situated white male offenders over the period studied. Hispanic male offenders sentences were 5.3 percent longer than their white counterparts.

This disparity held true in the period studied even when offenders received sentences below the range recommended by federal sentencing guidelines. Black men received below-range sentences 16.8 percent longer than similarly situated white men, while Hispanic men received sentences 10.6 percent longer.

The main disparity between white and black men is essentially consistent with the USSC's last report on the subject, which covered the time between Dec. 11, 2007 and Sept. 30, 2011. In that period, black male offenders had sentences 19.5 percent longer than similar white male offenders. There was no statistically significant difference between similar Hispanic and white male offenders in that period.

The report also found that women of all races were sentenced less harshly than white male offenders. White women received 26 percent shorter sentences; Hispanic women, 25.5 percent; and black women, 21.1 percent shorter. These rates still suggest a within-sex racial sentencing disparity, though one less pronounced than the male disparity. There are about 14,000 women in federal prison, mostly for drug-related offenses.

Whether or not an offender was a citizen had an impact on length of sentence; non-citizens had longer sentences. But education didn't make a difference: otherwise-similar offenders with and without at least some college education had the same length of sentence.

One factor did not turn out to be statistically significant: history of prior violence. Previous reports had not accounted for past violence, so the USSC collected relevant statistics information for FY2016. Controlling for violence, however, did not significantly explain the disparity between white and non-white offenders.

The USSC delimits its reports on sentencing disparity based on the dates of Supreme Court cases which have altered the use of federal sentencing guidelines. For example, the previous report covered a period following the deciding of Gall v. United States, which concerned the review of sentences outside those set by federal sentencing guidelines.

Part of the reason for this delimiting is to analyze the impact certain decisions have had on racial disparities in sentencing. The federal sentencing guidelines, which define ranges of sentences for federal crimes, were issued in 1984. The guidelines were meant, the Justice Department noted in 2006, "to emphasize fairness, consistency, punishment, incapacitation, and deterrence in sentencing."

A major blow was struck to the effectiveness of the sentencing guidelines in 2005's United States v. Booker, when the Supreme Court rendered the guidelines "effectively advisory" by severing two sections of the Sentencing Reform Act of 1984 for incompatibility with the Sixth Amendment's trial by jury requirement. What this meant remains murky, but in practice opened up a great deal of judicial discretion previously barred by the rationalized guidelines.

The federal sentencing guidelines impact on racial disparities is not fully clear. Several analyses have found that racial disparities persisted following the establishment of the guidelines, but prior to Booker. However, the USSC in a previous report found that the Booker decision led to a marked increase in the black-white male offender sentencing disparity: a 10 percent increase between the period following Booker and the preceding period under which the sentencing guidelines and the 2003 PROTECT Act drove the disparity down to 5.5 percent.

All of this contextualizes the USSC's most recent report, suggesting that the pronounced disparity between white and non-white offenders may be partially attributable to the lack of a strict, rational sentencing scheme. Such a scheme has been, since Booker, replaced by far greater discretion on the part of individual judges.

Attorney General Jeff Sessions has remained quiet on the issue of the murkiness surrounding sentencing guidelines. He did, however, draw attention in May when he instructed federal prosecutors to "charge and pursue the most serious, readily provable offense."

Sessions's order overturned one issued by his predecessor, Obama Attorney General Eric Holder, which encouraged prosecutors to exercise discretion when deciding on charges for certain low-level, non-violent drug offenders. Sessions, for his part, demonstrates a wariness of prosecutorial deviation from statutory norms, which may suggest some affinity for statutory over individual discretion.

"It is of the utmost important," Sessions wrote, "to enforce the law fairly and consistently."