WASHINGTON —  Only seven percent of the top staffers in the U.S. Senate are people of color, far below minorities’ representation in the population of the United States, according to a study released last week.

The report from the Joint Center for Political and Economic Studies found only 24 staffers of color out of the 336 top Senate staffers working in Washington. The Joint Center, a think tank that has focused primarily on issues affecting African-Americans, researched the top Senate jobs this past April.

Minorities make up over 36 percent of the U.S. population, and over 28 percent of the citizen voting-age population, the study said. Minorities are also under-represented among U.S. senators. There are two African-American senators, three Hispanics, and one Asian-American.

James R. Jones, who conducted the study, said researchers looked at top positions in senators’ Washington offices, including chiefs of staff, legislative directors, and communications directors in personal offices, as well as staff directors assigned to committees.

They were only able to find 12 Asian-American, seven Latino, three African-American and two Native-American staffers.

The top Senate staffers wield important influence with their bosses, and help shape legislation and policies that affect everyone, Jones said Tuesday. “You need to have people from all walks of life in the room making decisions,” said Jones, a Ph.D. candidate in the Sociology department at Columbia University.

Working for the Senate also opens doors to other jobs in government, and by not getting those first congressional jobs, minorities find it more difficult to move up a government ladder that looks favorably upon Capitol Hill experience, Jones said.

Minorities make up larger numbers in the Democratic Party than they do in the GOP, but the study noted that the number of minority staffers was not that different between the two parties. It found that 8.1 percent of the Democrats’ top Senate staffers were minorities and 6.7 percent of the top Republican staffers were minorities. The report said people of color make up about 37 percent of those who identify as Democrats, and nine percent of those who identify as Republicans.

“Increasing the presence of people of color in senior staff positions in the Senate will amplify the voices and perspectives of communities of color and in the process enhance the quality of legislative deliberations,” said Spencer Overton, president of the Joint Center.

The think tank is calling on senators to increase diversity by interviewing more minorities for top positions, hiring more minority interns and starting fellowships for minority staffers. It also called on the Senate to be more transparent in its staffing because – unlike many government agencies – Congress is not required to monitor the race and ethnicity of its workforce.

Researchers said they combed online profiles, consulted with Senate organizations and called Senate offices to come up with their numbers.