Drug policy has focused on a policing approach of prohibition and incarceration, which has contributed to spreading HIV within the injection-drug community. Comprehensive drug reform policies are showing better results. Despite massive investments in drug law enforcement in the past three decades, with much of the international interdiction effort paid for by the U.S. government through assistance to national military and police forces, there is "a general pattern of falling drug prices and increasing drug purity" throughout the world, according to the Vienna Declaration.