California Youth Crime Plunges to All-Time Low, a paper from the Center on Juvenile and Criminal Justice, analyzes recent data from the California Department of Justice’s Criminal Justice Statistics Center, and concludes that decriminalizing marijuana was correlated with an unheard-of 20% drop in the youth crime rate. The California youth crime rate is now the lowest it's been in recorded state history.
A large proportion of the drop in youth crime is directly attributable to a drop in arrests for possession of small amount of marijuana, but the rest seems to be a dividend from keeping kids out of the criminal justice system. That is, if you stop jailing kids for holding a little weed, they won't go to juvie and become career criminals.
California is still jailing some kids for holding, though, thanks to the provision in law that makes possessing marijuana in or near a school into a special offense.
Males said he suspects that many of the 5,831 marijuana arrests of juveniles in California last year may have occurred on school grounds. He doesn’t have data yet to check his theory, however.
In his police briefing, Males also notes that juvenile arrests in California were the lowest ever recorded since statewide statistics were first compiled in 1954. The decline, Males said, wasn’t due just to fewer marijuana arrests.
Drug-related juvenile arrests overall fell by 47 percent between 2010 and 2011. Violent crime arrests fell by 16 percent; homicide arrests by 26 percent; rape arrests by 10 percent; and property-crime arrests by 16 percent. Nationwide, according to the FBI Uniform Crime Reports, arrests of juveniles for all offenses decreased 11.1 percent in 2011 when compared with the 2010 number; arrests of adults declined 3.6 percent.