I've found this link to Radford statistics about serial killers and on page 14 it states that USA has more than 19 times the amount of serial killers than the second country on the list, which is England.

Is this just a statistical bias? Are the serial killers cases from other countries just never caught or maybe not even reported and therefore it looks like other countries have fewer serial killers?

It seems hard to believe that India and China, who combined have more than third of worlds population, "produced" only around 150 serial killers while USA has thousands.