Why were there so many serial killers in the 60s, 70s, and 80s?

I have no idea if this theory holds water, but for centuries, families used to police their own. Dad or Mom notice one of their kids hurting other kids, hurting animals, all the tell-tale signs and the next thing you know, that child died in a hunting accident, or drown in a creek, or was sent to an asylum or locked away in the attic.

Violent crime has been decreasing steadily since lead was removed from gas. It was an additive that Thomas Midgley Jr. came up with in the 1920s to stop engine knocking; however, the effects from lead-fume-spewing automobiles included violence and criminality:

"Use of leaded gasoline, which he invented, released large quantities of lead into the atmosphere all over the world.[30] High atmospheric lead levels have been linked with serious long-term health problems from childhood, including neurological impairment,[33][34][35] and with increased levels of violence and criminality in America[36][37][38][39] and around the world.[40][41] Time magazine included both leaded gasoline and CFCs on its list of "The 50 Worst Inventions".

His inventive resume includes chlorofluorocarbons. He had a knack for poisoning people and the planet.

R2 - Yes, and also the removal of lead-based paint that poor kids would eat the chips of, because apparently they are sweet like candy.

There has been a lot of research on this question. The reasoning is suspected to be as follows:

[quote]The serial killing phenomenon in the United States was especially prominent from 1970 to 2000, which has been described as the "golden age of serial murder."[43] The cause of the spike in serial killings has been attributed to urbanization, which put people in close proximity and offered anonymity.

[quote] The number of active serial killers in the country peaked in 1989 and has been steadily trending downward since, coinciding with an overall decrease in crime in the United States since that time. The decline in serial killers has no known single cause but is attributed to a number of factors. Mike Aamodt, emeritus professor at Radford University in Virginia, attributes the decline in number of serial killings to less frequent use of parole, improved forensic technology, and people behaving more cautiously.[44] Causes for the general reduction in violent crime following the 1990s include increased incarceration in the United States, the end of the crack epidemic in the United States, and decreased lead exposure in early childhood.[45][46][47]

The spike in the late 50s and 60s is also connected to development of the interstate highway system.

Legalization of abortion?

It's not just one thing. As r4 notes, the interstate highway system was a factor.

Also, before DNA testing became commonplace, it was easier to be an anonymous killer.

And in general, other changes in technology have led to the decline. I always think about the Yingying Zhang murder. Thirty years ago, the perp would probably still be out there, killing. With the help of technology, he was identified as a suspect within a week.

Not that lead was good for your health but I doubt that was a significant " element " in the making of serial killers. There have been eras lead was used for water pipes, food additives, dishware, and makeup.

With or without heavy lead expose we've always had serial killers. As indicated above I think we've just gotten a lot better at finding them. Plus with more urbanization it's become more difficult to to hide the bodies proving the murder happened in the first place.

Yes, I think R6 is onto something. There could have been serial killers all over the place in the 19th century, but unless they were as showy in their MO as Jack the Ripper, the technology to notice that the murders were being done by one person wasn't there. If they travelled across state lines there were no comms systems by which new cops could identify an MO. Policing wasn't even a serious thing till well into the 19th century, and process-driven detecting came much later, never mind your DNAs, black lights etc.

Likewise, there could be just as many serial killers today, but they're being scooped up before they can properly earn the title.

We certainly know there were (proportionately) as many psychopaths in the 19th century as there are today, because the majority of them end up in high positions in finance and corporates rather than in a jail cell. If you think the Gilded Age happened with a dearth of psychopaths you might like to buy this railroad.