Some 13 million U.S. drug users spent approximately US$ 67 billion on illicit drugs in 1999, making the U.S. market the most lucrative one in the world for Colombian traffickers. Washington spent roughly two-thirds of its US$ 17.8 billion 1999 anti-drug budget on interdiction and related activities to curb the flow of illicit drugs from Colombia and elsewhere in the hemisphere into the United States. Indeed, throughout the 1990s the U.S. government placed heavy emphasis on interdiction activities as a key tactic in its overall strategy in the war on drugs.