According to some sources, the percentage of serial killers who are African American is estimated to be between 13 and 22 percent.[75][76] Another study has shown that 16 percent of serial killers are African American, what author Maurice Godwin describes as a “sizeable portion”.[77] However, the 2013 Radford/FGCU Serial Killer Database annual statistics show, for the decades 1900–2010, that the percentage of African American serial killers is 40.7%
I have to wonder how that Radford study identifies someone as a serial killer, since he includes killers with as few as two victims and gives, among the motives, “financial gain” and “gang related.” Someone who shoots a couple of rival drug dealers doesn’t really constitute a serial killer in most people’s minds.
Depends to a considerable extent on your definition of “serial killer.”