America’s incarceration rate is in decline

>Rapidly declining numbers of youth are committing crimes, getting arrested, and being incarcerated. This matters because young offenders are the raw material that feeds the prison system: As one generation ages out, another takes its place on the same horrid journey.

Another factor which will soon impact this, if it isn't already, is the rapidly changing nature of youth. Fertility rates have been dropping since 2009 or so. Average age of parents is increasing. Teen pregnancy on a long and rapid decline.

All of these working together means that each year the act of having a child is much more deliberate and the parents likely having more resources. Which in turn should mean fewer youth delinquency, which as the article notes is how most in prison started out.

It's lead.

Lead concentration in America "rapidly increased in the 1950s and then declined in the 1980s" [1]. There is a non-linear discontinuity among kids born in the mid 80s, with linear improvements through to those born in the late 2000s [2].

Arrest rates for violent crimes are highest from 15 to 29 years old (particularly 17 to 23-year olds) [3]. They're particularly low for adults after 50 years old.

We're around 40 years from the last of the high-lead children. 17 years ago is the late 2000s.

[1] https://www.sciencedirect.com/science/article/abs/pii/S10406...

[2] https://ehp.niehs.nih.gov/doi/10.1289/EHP7932

[3] https://kagi.com/assistant/d2c6fdd5-73dd-4952-ae40-1f36aef1e...

I think lead is nasty stuff, but if it was the single cause of high crime, surely we'd see a similar effect in other domains, like a rebound effect on IQs (another thing lead was blamed for)?

Instead the Flynn Effect seems to have been strongest during the era of high lead, and it's tailing-off now.