Serial killers have been dwindling in numbers since hitting their peak in the 1980s, the world's leading serial murderer database has shown.
In the 1990s, forensic psychology teacher at Radford University Michael G. Aamodt began setting his class a task: creating a profile of serial killers, including a timeline of their murders, their life history, basic demographic information, and information about their crimes. At first, the projects were stored in a drawer, being added to the class website years later. Eventually, the information was transferred to a database – and it became a project of its own to update and maintain the most comprehensive database on serial killers through the years.
Using the FBI definition of serial killers (people who unlawfully killed two or more victims in separate events) the researchers from Radford University and Florida Gulf Coast University have documented killers from around the world, with some pretty interesting findings.
For instance, the US is the country with the most recorded serial killers, at 3,613 since the year 1900. That's 67 percent of the world's serial killers, for a country with 4.35 percent of the world's population. The next closest is England, with 167. Japan (137) South Africa (123), India (121), and Canada (119) are the only other countries where there have been over 100 serial killers identified by the database.
Since the start of the data in 1900, approximately 11 percent of serial killers have been women, with the percentage of female serial killers going down over the years in comparison to men. Before the 1930s, roughly a third of serial killers were women, going down to around six percent since 1980. Female serial killers were more likely to use poison than male serial killers, and to kill for financial gain as a primary motive. Male serial killers, meanwhile, were more likely to kill for their own enjoyment, and more likely to do so by shooting or strangling their victims. Victims of female serial killers are more likely to be family, rather than male serial killers who tend to kill non-family members.
Breaking down the crimes further, the database has some other pretty grim facts. This includes information on whether the serial killer ate their victims (about 1.8 percent of male serial killers did, compared to 1.3 of female serial killers), whether necrophilia occurred (3.4 percent of male serial killers did this, versus 0.4 percent of female serial killers) and whether they drank their victims' blood (0.7 percent of male serial killers and 0.4 percent of female serial killers).
One strange thing shown by the data is the decline in killings by serial murderers in the United States since the absolute peak of the 1980s: 404 victims in 1987 alone. During the 1980s, there were 150 serial killers who had killed two or more victims and 104 who had killed three or more victims.
There has been a sharp decline since, with 138 serial killers who killed two or more victims in the 1990s, and 89 who had killed three or more. Fast forward to 2010-2018 (the last year with complete data in the database at the time of the last update) and there were just 43 serial killers in those years that had killed two or more victims, and 23 who had killed three or more.
The researchers put this decline down to several factors. Part of the decline could be that better detection by law enforcement (for example, on insurance fraud) means that serial killers with financial motives are less likely to go undetected, and so are either caught before meeting the definition of a serial killer or are put off murdering for financial gain entirely.
There has also been a decline in opportunity for seasoned serial killers, and potential serial killers seeking their first victim.
"Stricter parole policies have put fewer potential serial killers back on the streets," the team write in the 2020 report. "Since 1950 in the Unite[d] States, 16.8% of the serial killers in our database killed again after being released from prison for a prior homicide. This figure, combined with the fact that 79% of U.S. serial killers spent time in jail or prison prior to their first murder, supports the relationship between longer prison sentences and decreased serial killer frequency."
Opportunities have also gone down since the decline of hitchhiking.
"There is a decreased availability of high risk targets for serial killers. That is, there are fewer people hitchhiking, offering rides to strangers, and walking to school," the team continued. "Some of the largest decrease in serial killer victim types from 1980-1999 to 2000-2017 are: Hitchhiking related, abductions from shopping centers, and disabled motorists or good Samaritans."