Anti-racism groups say the problem represents structural racism.
The problem is especially acute in smaller towns, The New York Times reported on Tuesday.
Based on data from a federal survey of police departments in 2007, the newspaper reported, ''nearly 400 departments, most with fewer than a hundred officers'' were ''substantially whiter than the populations they served. In these departments, the share of white officers was greater than the share of white residents by more than 50 percentage points.''
In Ferguson, only four of the 53 officers are black, according to the police chief. But big cities too face an over-representation of white officers, relative to the resident population.
In New York, Philadelphia, Chicago, Dallas and Houston ''white officers vastly over-represent the share of white residents'' reported Bloomberg last month.
While anti-racism groups ascribe the unbalance to institutional or structural racism, police departments often dismiss the problem or say it is hard to find qualified officers among minority groups—a response which confirms their judgment, say anti-racism campaigners.
Beside prejudice against racial minorities in the hiring process, racism in other key institutions, such as education and income distribution, acts as a barrier to non-whites entering the police force.
But, achieving a better racial representation is possible ''If the leadership, if the police chief, is dedicated to getting more diversity in the work force,'' said Nelson Lim, a senior sociologist at the RAND Institute’s Center on Quality Policing.
Cleveland Heights—with a 40 percent black population—seems to be more committed to diversity in its police force than is usually the case.
The town has two types of officer positions, one requiring a college degree and one, called basic patrol, that does not. ''Once a basic patrol officer is hired, the city will reimburse tuition costs, and many eventually earn a degree and work their way to the upper tier,'' said The New York Times.
The approach helps members of racial minorities—who are overrepresented in poverty statistics—overcome their inability to afford education.
Police brutality against racial minorities has gained attention over the past weeks after a white officer shot dead Michael Brown, while the black teen was holding his arms up in surrender, according to testimonies.
The shooting sparked nation-wide anti-racism protests.
Anti-racism campaigners have accused the Ferguson police of ''militarization'' after the force used attack dogs, assault rifles and armored vehicles to disperse Black residents who were protesting against Brown's killing. At least one man was shot during the police crack-down.