It is insane to just confidently assert that the only factor in the decrease in crime is Lead. Treating an insanely nuanced issue as an absolute doesn't make your argument more compelling, it is actually kind of baffling.
The 1st recorded cases of fatty liver disease and T2D in children were in the 1980’s are have continued growing since - lead must have been protecting children’s health.
Testosterone has been on a sharp decline during this same time period - lead must promote healthy testosterone production.
Debt of all kinds, from the national debt, to household debt, to student loans debt has increased exponentially and consistently with lead removal - lead must promote financial literacy.
There are many factors that correlate and potentially contribute to a reduction in incarceration rates.
There are estimated 1.8-1.9M incarcerated. Since 1980 to the present there are well over 1M violent crimes (rape, murder, aggregated assault, robbery) per year. Let’s look at another factor that might contribute to falling incarceration rates that tend to explain this discrepancy in incarceration vs total crimes…conviction rates:
Murder: ~57.4% in 1950 vs. ~27.2% in 2023—a ~2.1x difference.
Rape: ~17.3% in 1950 vs. ~2.3% in 2023—a ~7.5x difference.
Aggravated Assualt: ~19.7% in 1950 vs. ~15.9% in 2023—a ~1.2x difference.
The neurological effects of lead don’t tend to explain away falling police clearances nor convictions.
Kevin drum and Rick Bevin both did a ton to lay this out systematically.
As leaving drum has noted, Lead is NOT the only contributor to crime, but it was the cause of the largest variations for most of the 20th century.
https://en.wikipedia.org/wiki/Crime_drop#Decline_since_the_e...
Maybe they were doing similar things with lead or something else is a big factor. Perhaps the rise of ever more cheap entertainment for young males who are most likely to commit crime. That's a global thing.
Were the older people who grew up with lead exposure also experiencing higher rates of impulsive crime in the late >1990s relative to the new and prior generations? That would help eliminate the major differences in economics/culture/politics of their upbringing (for ex: mass flight of families moving to the suburbs to raise their young kids after the 1970s crime wave scared them away).
Bad decisions like these get less common with age, partly because of consequences (jail, death, etc), partly because getting up to no good requires free time, ambition and freedom, all of which are in shorter supply with age and the resultant responsibilities competing for every individual's supply of these resources.
So if the replacement cohort of people who are coming into prime crime age decline to participate at the same rates the crime rate goes down.