Total # of serial killers in USA history?

Does this site or any other reputable site list the total number of serial killers in US history?

I read in a book of mine that there have been over 800 serial killers in the US in just the last 25 years!! That number included murders that the police knew were serial killings but never found the killers. But still that sounds very high (though I suppose it wouldn't shock me if it were true).

I'm not looking for stories so much as I am stats.

Anyone know where I can find a truly accurate count?


Signing off,
AgentX