California's teenagers can no longer be considered a high crime demographic, following a decades-long slide in youth crime and arrest rates, according to a new study.

The Center for Juvenile and Criminal Justice has released a report looking at California's youth arrest rates and rates for various types of crime and found 2016 continued a decades-long decline in both.

"A lot of people still think in terms of 25 or 50 years ago when younger people had higher crime rates than they do today," said Mike Males, a sociologist and senior researcher for CJCJ. "Today, teenagers and young adults are not a high crime population anymore; it's really shifted into the late twenties and thirties and forties."

That shift came as California largely moved away from incarceration as a preferred punishment for youth. Incarceration rates have gone down on the state and county levels.

The arrest rate for 10- through 17-year-olds for violent crimes dropped 73 percent between 1990 and 2016. Since 2007, the overall youth arrest rate has set record lows each new year. Millennials had the lowest youth arrest rates of any generation, while Baby Boomers had the highest.

Males said the exact reason for the decline is hard to sort out, but there's evidence that younger generations have not struggled with illicit drugs as much as older generations.

"The rest of it we really don't know because we haven't improved poverty conditions that young people live under, we haven't improved a lot of the domestic violence situations that children face," he said. "So really a lot of the decline in juvenile crime remains a mystery."

Youth are now also more likely to graduate from high school and college, though Males said it's unclear why educational attainment has also increased.

He said, if anything, it seems that younger generations may be reacting against their parents.

"And their crime problems and the fact that young people have to take responsibilities at younger ages," he said.

Overall, he said, more research is needed to figure out exactly why youth crime has declined, and how to create policies that reinforce the positive trend.