Recent reports on USA prisoners and jail inmates in 2021 show youth incarceration is still heading toward zero. The prison incarceration rate for men ages 18-19 fell 88% from 2001-2021. The trendline for that decline hits zero in 2025.

The number of juveniles in adult prisons fell 92% from 2000-2021, and juveniles in adult jails fell 79% from 1999-2021. Trendlines for juveniles in adult jails and prisons hit zero in 2025 or earlier.

From 2001-2021, male incarceration rates also fell 70% for ages 20-24, 52% for ages 25-29, 38% for ages 30-24, and 22% for ages 35-39, with steeper declines for Black males. But the male incarceration rate rose 9% for ages 40-44, despite a 25% decline for Black males ages 40-44. 

The 2001-2021 change in male incarceration rates reflect arrest rate trends by age. From 1988-2020, property crime arrest rates fell 94% for ages 0-14, and 82% for ages 18-20, but fell just 7% for ages 50-54. From 1994-2020, violent crime arrest rates fell by 82% for ages 0-14, and 67% for ages 18-20, but rose 20% for ages 50-54.

It is remarkable – and exasperating – that the debate over crime and incarceration almost entirely ignores divergent trends by age. Youth crime and incarceration are vanishing as arrest and incarceration rates are still increasing for adults over 50. The only crime theory that explains this divergence is the impact of birth year trends in preschool lead exposure. 

• The increase in arrest rates for adults over 50 compares adults in 2020, born near the circa-1970 peak in leaded gas emissions, versus adults over 50 in the late-1980s and early-1990s, born before the surge in leaded gas use after World War II. 
• The massive fall in youth arrest rates compares youths in 2020, born after the phaseout of leaded gasoline, versus youths in the late-1980s and early-1990s, born near the circa-1970 peak in leaded gas emissions.
• The steeper decline in Black incarceration rates since 2001 reflects the fact that Black children recorded steeper blood lead declines associated with slum clearance over the 1960s and city air lead declines since the early-1970s (explained here).

It is especially exasperating that criminal justice reform advocates ignore incarceration trends by age. Those trends should inform incarceration reduction strategies, to have the greatest impact and to generate the least resistance from “tough-on-crime” advocates. 

We do not have a “mass incarceration” problem for youths. Not anymore. Reductions in preschool lead exposure have caused massive declines in youth crime and incarceration. We do still have mass incarceration for adults over 50, and it’s getting worse. Data for older age groups, first reported in 2007, show that male incarceration rates from 2007-2021 fell 5% for ages 45-49, but rose 23% for ages 50-54, 66% for ages 55-59, 79% for ages 60-64, and 87% for ages 65 or older.

Many studies show that older adults released from prison have much lower recidivism rates than prisoners released at a younger age. A 10-year follow-up of state prisoners released in 2008 found that 78.6% of prisoners released at ages 24 and younger were convicted of another offense within 10 years after their release. But the reconviction rate for prisoners released at ages 55-64 was 36.3% and the reconviction rate for prisoners released at ages 65 and older was 26.5%. 

The fastest growing segment of the U.S. prison population has the lowest recidivism risk. That is where incarceration reduction advocates should focus their efforts.