After decades of increasing incarceration of blacks, a new trend at U.S. prisons is emerging, particularly among women, according to a new report from a Washington-based criminal justice watchdog.

The Sentencing Project report, released February 27, found that the black-to-white incarceration ratio has declined 16.9 percent for men and 53 percent for women from 2000 to 2009, the most recent year the group examined. During that period, the incarceration rate rose 8.5 percent for white men percent and 47.1 percent for white women, while it fell 9.8 percent for black men and 30.7 percent for black women.

In 2009, prisons still had more black males than members of any other race, but whites were the biggest racial group among female prisoners.

Marc Mauer, The Sentencing Project’s executive director and author of the study, said the change in the black-white incarceration rate for females is "dramatic." In 2000, black women were put in prison at six times the rate of white women.

"It’s encouraging for me to see the declining rate of black women incarceration," he said.

Several factors may play a role in the changing numbers, Mauer said. The decline in black female incarceration could stem from changes in crime, law enforcement, sentencing practices and socioeconomics, among other factors, he said. The falling number of drug incarcerations also could be a contributing factor.

As for white women, socioeconomic factors and more methamphetamine-related prosecutions could be to blame.

"This report has explored the factors which may be contributing to these trends," Mauer wrote in the study, "but is clearly just a first step in such an analysis."

Contact Andrew Ramonas at aramonas@alm.com.