As of the mid-2000s, an American convicted of a federal crime is 7 percent more likely to be sentenced to prison time if they are black than if they are white, new research shows. That jail time is likely to be eight months longer if the person is black, according to 2016 data.

That’s a major disparity, but it’s also a major improvement over where we were 20 years ago, according to an analysis presented at the American Sociological Association earlier this month.

Ryan King, one of the lead authors on the paper and a professor and chair of sociology at The Ohio State University, told Living Lab Radio those results were not expected. But there were some reasons to suspect the gap may have shrunk, he said.

First, according to the General Social Survey, the number of people who support segregationist policies has declined since the 1970s. Second, there is more diversity in the legal profession. Research shows that more diversity in the courtroom workgroup is correlated with more equality in sentencing, King said.

And perhaps most significantly, in 2009, leadership at the U.S. Justice Department changed.

“You have a change in the presidential administration, you have the first African-American attorney general in Eric Holder, and there's a different take on mandatory minimums and drug charges in federal court,” King said.

“One year later, in 2010, Congress passes the Fair Sentencing Act and that gets incorporated into the sentencing guidelines,” he said.

“And so, we think it's probably not coincidence that … you see almost all of the decrease in sentencing disparities, particularly for drug cases, happen in the five or 10 years following that legal change and that change in the administration,” he said.

In 1992, blacks were sentenced to 40 months more prison time than whites. That gap narrowed to about 30 months in the early 2000s. It wasn’t until 2009 when a rather stark decline began.

“By 2016, the last data point in our analysis, it was … below 10 months,” King said.

The point of the research is not to say that sentencing disparities between blacks and whites is solved, King said.

“Rather, we just wanted to describe the change over as long a period of time as we could,” he said. “There's not perfect equality in sentencing. We are not yet at parity, and so there's still work to be done.”