I can certainly believe that the United States has 85% of the world’s “recognized” serial killers (meaning serial killers either caught or whose existence was realized by authorities–for example Ted Bundy was caught whereas the Zodiac Killer or Jack the Ripper were known but never caught.) The problem is I think a lot of serial killers can fly under the radar. Read about say, the Green River Killer, it actually was many, many murders into his crime spree before authorities realized they were dealing with a bona fide serial killer and not just dead prostitutes murdered by various Johns.

When your victims tend to be people that typically aren’t kept track of (like prostitutes, for example) then it can take longer to ever discover there is a serial killer at work. Even still, most experts believe there are at least several unsolved disappearances/murders out there that can be attributed to already caught serial killers (like Ted Bundy) but for whatever reason they’ve just never been able to link them up conclusively.

Imagine a serial killer who travels over a wide geographic area (like Bundy did) and who doesn’t do anything to specifically draw attention to himself (like say, the Green River Killer) and it’s easy to imagine serial killers in third world countries who are totally off the radar.