Not just in the US. Also in Europe and most of the developed world. Violence peaked in 80's - 90s and then started to decrease dramatically.
Lead–crime connection is the strongest explanation. Past lead exposure functions as a predictor for criminal activity. Crime starts to drop in every country after the use of leaded gasoline is forbidden.
More interestingly, we also have cross-national natural experiments, where different countries banned lead gasoline at different times, and the timing of drops in the crime rate is pretty spot-on
Allowing abortion in the US did not change anything in other countries. Crime rates have dropped in every country shortly after leaded gasoline was phased out.
The peer-reviewed science says that legalized abortion accounts for about 20-30% of the crime reduction we have seen. (Reference: The Wikipedia article I already linked to in the grandparent post)
While the lead theory may indeed be true, one other thing has changed in almost all areas of the world.
Birth rates.
And with declining birth rates, comes a decline in the number of youth, meaning "more of the population" is of an older age. Men are typically at their most aggressive when young adults, and those which have started families, have a different perspective on life.
Note: not saying the above is the cause, but I do believe it to be a valid theory.
edit: it is also plausible that multiple things cause one effect.
That's caused by providing at least somewhat decent sexual education in schools, although the US is still lacking in mandating sex ed or mandating medically accurate sex ed (=banning "abstinence only").
Are you sure? It could just as well be because of the internet catching our attention so boys and girls don’t spend it on each other like they used to. No evidence for either claim although both sound plausible
Teen pregnancy is heavily studied, it is big social issue. It has pretty large impact on mother, child, father and extended family. The articles I have seen strongly associated sexual education with both less sex and safer teenage sex.
Basically, if you teach kids about sex and anticonception and condoms, they are less likely to do it and more likely to use this condoms and generally behave more safely.
On the other hand, abstinence only education is associated with more pregnancies.
That parenthood out of wedlock is a tragedy is true, but how can you or said articles authors be sure the link between teens today not having them being because of sex ed in school? I’m not saying it’s unlikely, but I’m wondering if there is any evidence showing the correlation, or if the effect is due to any other reason?
https://www.motherjones.com/kevin-drum/2013/08/murder-rate-d...