After a huge dropoff with the ending of the crack wars around 1995, the black homicide perpetration rate has turned up again in this decade. For black male 14-17 year olds, according to tables prepared by James Alan Fox of Northeastern U., the number of homicide perpetrators in absolute terms is up 34% from 2000-2001 to 2006-2007, up 12% for black 18-24-year-0lds, and up 17% for blacks men 25+.
Here in LA, there was a spike in Hispanic gang murders after Villaraigosa was elected mayor in 2005, but the LAPD remains in the capable hands of William Bratton, and that has faded out.
My assumption is that technological trends, especially the spread of cellphones and cellphone cameras, has made crime a riskier business, so crime rates should be dropping all else being equal.
When I debated economist Steven Levitt over crime in Slate in 1999, he asked me what my prediction for future crime trends was: I replied that I figured that black teens are currently benefiting from the example of their many older brothers and cousins whom the crack wars left in jail, wheelchairs, or cemeteries, but that eventually a new cohort of black teens would come along without direct experience of the horrors of crack wars of 1988-1994, and the homicide rate would go back up again.