The information about the ATF, its staffing and criminal enforcement efforts, 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, electronic and hardcover publications of the Bureau of Alcohol, Tobacco and Firearms (including a special computer run prepared by ATF for TRAC); 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; internal records, electronic and hardcover reports of the Office of Personnel Management; internal records, electronic and hardcover reports of the General Accounting Office, the Congressional Authorization & Budget Submissions as well as Congressional hearings. Basic population figures came from the United States Census Bureau.