America’s incarceration rate is in decline

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.

But it's so satisfying to one's ego that a single cause is the issue. All complexity of societal changes in the last 50 years can be outmanuevered. Simplification is sexy.

There was a crime decline in many rich countries from the 1990s as well.

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.

Why bother stopping at crime rates with that confidence?

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.

If you do the same comparison of the rates of leaded gasoline during childhood to adulthood crime rates across different countries which have different histories of leaded gasoline usage, you notice that the correlation persists. While of course correlation does not imply causation, it's a link that's fairly well-established in literature, it's not a spurious correlation, and we know that lead has concrete neurological effects, so it's plausible from a pharmacological basis.

Yes, leaded gasoline was being banned in many rich countries at about the same time, and there's a positive correlation between the year it was banned and the year that violent street crime began to decline.

Since 1970 testosterone has declined 1% per year and it’s well established higher testosterone is linked to impulsive and violent criminal behavior and in countries like the US crime rate is at a 50 year low correlating with this decline starting 1970.

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.

So reducing lead exposure immediately changes your brain to do less crime?

No, there's an offset of about 18 years, if I remember correctly?

There have been a lot of studies that show the correlation with lead up and down and varied by lead in different cities countries with different phaseout timelines.

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.

I see, so since a large majority of crime is done by young people, peaking between 15-25, they are basically comparing a whole new generation of kids who didn't have developmental brain issues vs their elders.

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).

It’s satisfying to know that we’ve eliminated a major environmental toxin with so many awful effects. It doesn’t mean that lead explains everything, but it is a lot better than the “we built enough prisons to lock up all the bad guys, maybe we should build more” alternative hypothesis/proposal I’ve heard.

Where are these conviction rate statistics from? What are they measuring? (is it reporting of crime to a conviction on that crime?)

That's an interesting question, and I don't know the answer.

Kids that grew up huffing leaded exhaust are more bad decisions inclined than they would otherwise be. It's not just crime. The most heavily leaded cohort in the US is also known for drunkly crashing their muscle cars and wasting their youth smoking pot in a commune.

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.