The FBI, criminologists, and sociologists credit many factors for the 38% decrease in violent crime since 1991, including improvements in the criminal justice system, law enforcement policies, and the economy, a reduction in the "crack" cocaine trade, and the aging of gang members. Gun control advocates claim that gun control is responsible for the decrease in crime, but since 1991 gun control has been scaled back the federal, state and local levels, and the number of privately owned firearms has increased between 65-70 million.