The link I provided, http://www.khazaria.com/genetics/abstracts-cohen-levite.html, is simply a page that has collected a bunch of sources and put excerpt quotes from these various sources (so khazaria.com itself is not making these claims they are simply citing people). 

 "Based on surveys of Jewish cemetery gravestones, priests represent approximately 5% of the estimated total male world Jewish population of roughly 7 million" an excerpt from: Michael F. Hammer, Karl L. Skorecki, Sara Selig, Shraga Blazer, Bruce Rappaport, Robert Bradman, Neil Bradman, P. J. Warburton, Monica Ismajlowicz. "Y Chromosomes of Jewish Priests." Nature 385(6611) (January 2, 1997): 32-33. 

 Again someone should include something about what the estimates are for the amount of Jewish males with the last name Cohen (modern "Cohanim") should be given, especially as the section of Levites notes Ashkenazi Levites are again thought to be make up about 4% of the overall Ashkenazi population.