There's been a huge shift in the racial makeup of U.S. prisons in the past decade, The New York Times reports.

The Sentencing Project analyzed prison populations from 2000 to 2009, finding the rates of incarceration for blacks dropped sharply during that period: 30.7 percent for black women and 9.8 percent for men.

The report also found a major spike in incarceration rates for white men and women during the same period, according to The Times. The rate for white women increased 47.1 percent for white women and 8.5 percent for white men.

Rates of incarceration dropped slightly for Hispanic men but jumped 23.3 percent for Hispanic women.

A dramatic shift in a prison population is highly unusual, the Sentencing Project's director Marc Mauer told The Times. From the Times:

"But the trend is clear, Mr. Mauer said, adding that no single factor could explain the shifting figures but that changes in drug laws and sentencing for drug offenses probably played a large role. Other possible contributors included decreasing arrest rates for blacks, the rising number of whites and Hispanics serving mandatory sentences for methamphetamine abuse, and socioeconomic shifts that have disproportionately affected white women."