Updated

Blacks in the United States are imprisoned at more than five times the rate of whites, and Hispanics are locked up at nearly double the white rate, according to a study released Wednesday by a criminal justice policy group.

The report by the Sentencing Project, a Washington-based think tank, found that states in the Midwest and Northeast have the greatest black-to-white disparity in incarceration. Iowa had the widest disparity in the nation, imprisoning blacks at more than 13 times the rate of whites.

Such figures "reflect a failure of social and economic interventions to address crime effectively," as well as racial bias in the justice system, said Marc Mauer, the group's executive director.

Vermont, New Jersey, Connecticut and Wisconsin incarcerated blacks at more than 10 times the rate of whites, the group said, citing Justice Department statistics from 2005. Vermont had a ratio of 12.5, followed by New Jersey with 12.4 and Connecticut with 12.

States with the lowest black-to-white ratio were Hawaii, with 1.9, Georgia with 3.3 and Mississippi with 3.5.

In Iowa, blacks are imprisoned at a rate more than double the national average. For every 100,000 people, Iowa incarcerates 309 whites and 4,200 blacks, the study said.

Paul Stageberg, administrator of the Iowa Division of Criminal and Juvenile Justice Planning, said the results are not surprising, but the causes are subject to interpretation.

He said the state's disproportionately high black arrest rates are likely linked to high poverty rates among blacks and lower educational achievement.

In 2001, a governor's task force released a report that said 24 percent of Iowa prison beds were occupied by black inmates even though blacks comprised just over 2 percent of the state's population.

The group that compiled Wednesday's report made several recommendations such as reviewing federal drug laws and giving judges more discretion to decide sentences rather than imposing mandatory minimum prison terms.