The information about the DEA, its staffing and criminal enforcement efforts, and federal drug enforcement more generally was compiled by TRAC from a variety of sources. The sources included computerized data obtained under the Freedom of Information Act from the Justice Department and from the United States Office of Personnel Management. These data were supplemented by interviews with current and former government officials, attorneys, and agency data processing specialists. Additional information was drawn from internal administrative records and hardcover publications of the Drug Enforcement Administration; internal administrative records and statistical reports of the Justice Department; electronic databases, internal records and hardcover publications of the Administrative Office of the United States Courts and the U.S. Sentencing Commission; internal records and published reports of the Office of Personnel Management; internal records and published reports of the General Accounting Office, the Congressional Authorization & Budget Submissions as well as Congressional hearings, and reports by the White House Office of National Drug Control Policy. Basic population figures came from the United States Census Bureau.