The economics of bootlegging was one factor underlying cooperation. Bootleggers needed stable business relations with other bootleggers, exporters, shippers, manufacturers, processors, and retailers. They also developed mutually beneficial relationships with the police and politicians. However, the bulkiness of alcoholic beverages, the ease of hijacking other bootleggers' supplies, and the efforts to protect or establish territorial monopolies resulted in the use of violence. Thus, many unknown young men became successful bootleggers, and many legal businesspeople abandoned the liquor business from fear of the violence. When prohibition ended some bootleggers became legal liquor dealers while others remained important underworld figures, using the lessons learned about cooperation and violence. The violence of bootleg liquor and that associated with illegal drugs today have many similarities, although the drug-related violence results from different political and economic forces. Government policies and the ease of concealing of heroin and cocaine combine to create the major sources of violence in drug dealing. The fear of law enforcement and harsh penalties creates a high level of anxiety and mistrust among drug dealers, resulting in the threat to use violence to enforce silence and discretion. The policies thus may have increased the degree to which drug dealing has been controlled by people willing to kill for profit. Reference notes.