Serial killers and their tantalizing mysteries are the things of nightmares and cautionary children tales. But the reality is, documented cases of serial killers in the United States are decreasing, and it's unclear why that is.

Serial Killer Statistics Over the Decades

Virginia’s Radford University and the Florida Gulf Coast University have compiled an online database that has tracked serial killer statistics both in the nation and internationally. The database defines a serial killer as someone who unlawfully takes the life of two or more individuals in separate events.

According to their data, serial killers in the United States peaked around the 1980s but have been dropping ever since. During the 1980s, there were 768 serial killers as compared to 117 in the first half of the 2010s.

Additionally, serial killers with victims of two or more and three or more are both dwindling. During 2010 - 2015, there were 54 serial killers who killed two or more individuals compared to 145 in the 1980s, whereas only 29 serial killers killed three or more individuals in 2010-2015 compared to 102 in the 1980s.

When broken down by race, the numbers do change between the decades. In the 1980s, 53% of serial killers were white as compared to 36.8% who were black. However, in the most recent years of 2010-2015, the numbers seem to almost flip, with 30.8% of serial killers being white while an overwhelming 59.8% were black. Overall, however, serial killers in the United States remained predominantly white over the past century, with 51.7% of serial killers being white, 39.8% of serial killers being black, and the remaining being either Hispanic, Asian, or Native American.

Motives Behind Serial Killings

It's also interesting to look at the motives behind serial killings revealed in the university studies. Within the United States, 31.76% of serial killings happen because killers gain some sort of enjoyment from it, whether it be the power, lust, or thrill they get out of it. While killing for enjoyment is the main motive for serial killers in the nation, it is closely followed by killing for financial gain at 30.14%. Anger follows third at 18.07%, and multiple motives rank fourth at 9.81%. On the data provided by the two universities, the United States remains one of the highest producers of serial killers, with 3,204 serial killers documented in the past decade before 2016. However, the database does indicate that some caution should be reserved in the numbers because the data only reflect the numbers of serial killers caught and those that have been reported by police.

Why Have Serial Killers Stopped Killing?

With the basic frameworks of who serial killers are and what drives them, the question remains, why have cases of serial killers within the nation dwindled by nearly 1/7th since the 1980s? An in-depth analysis by Discover Magazine highlights a few plausible speculations as to why the numbers have decreased.

One of the most plausible speculations is the fact that developments in science and technology have tightened the reins on serial killers getting away with their crimes. In the past decade alone, technological advancements in DNA analysis have helped track down some of the most elusive serial killers of the past. The most notable case is that of Joseph DeAngelo, the notorious Golden State Killer whose calculated rapes turned into the vicious murders of 12 women between 1976 and 1986. It was not a misstep of DeAngelo that led to his capture, but rather a DNA sample from a relative that was submitted to a genealogy mapping company.

In another concrete explanation, some researchers suggest that longer prison sentences and stricter parole measures for those who have already committed murder have helped reduce the potential that an offender repeats. And this automatically disqualifies them from meeting the serial killer definition of two, three, or more kills.

Other researchers point to a shift in the way society perceives safety nowadays. In the decades that produced serial killers, including Ted Bundy and John Wayne Gacy, parenting methods looked a lot different than they do now. A main difference is the rise in “helicopter parenting,” a method in which parents are always involved in nearly every aspect of their child's life. This type of parenting makes it difficult for children to develop unhealthy behaviors that serial killers often exhibit in their formative years.

There is also the reality that maybe larger numbers of serial killers exist, but they are simply getting away with their crimes. According to the FBI, just over 60% of all homicides in 2018 went unsolved. This means that contrary to popular belief, there is almost a 50% chance that someone who commits a murder might get away with it. And with the intentional detail of the crimes committed by serial killers, it is plausible to consider that maybe the numbers of serial killers are dwindling simply because serial killers are getting better at not leaving a trace behind.

This particular speculation has the support of Thomas Hargrove, the founder of the Murder Accountability Project. Hargrove explains, “We know that serial murder is more common than is officially acknowledged. Serial murders tend not to be solved. They’re good at killing.” According to the Murder Accountability Project, there may be as many as 2,000 serial killers still at large.

While there certainly is no lack of speculation as to why serial killings have decreased over the past couple of decades, what has become clear is that advancements in technology, investigative practices, and even the internet have made it incredibly difficult for the truth to remain hidden. Cracks in ciphers like the one left behind by the infamous Zodiac killer and DNA advancements may only make it a matter of time before unknown serial killers of the past are brought to justice.