ATF is responsible for Federal regulation of the alcohol, firearms, and explosives industries and enforcement of the related criminal statutes. ATF investigated more than 2,272 incidents involving explosives in 1976. ATF is also the lead agency in the development of an explosives tagging program, in which explosives will be tagged with additives that can be detected before detonation and identified after explosion. In addition, ATF licenses nearly 165,000 dealers, manufacturers, importers, gun collectors, and ammunition makers and regulates the manufacture, importation, and sale of over 6 million firearms annually. Since ATF employs only 4,000 people, most investigation of gun crimes is conducted by the more than 500,000 State and local law enforcement officers. ATF's four basic enforcement strategies released to firearms are (1) the direct investigation of firearms violations, (2) assistance to State and local law enforcement officers through training efforts, the tracing of firearms through the national firearms tracing center, and the provision of information about the type and source of firearms used in specific local jurisdictions, (3) special projects and studies to develop information about firearms used in crime; and (4) regulation of the firearms industry. Since 1976, the Concentrated Urban Enforcement program has brought all four of the basic strategies together in concentrated areas. A preliminary evaluation has concluded that CUE has contributed significantly to a reduction in major crimes involving firearms as well as illegal firearms trafficking in the Washington, D.C., area.