Doesn't that stat just mean that >99.9% of population has not been murdered. It says nothing to the number of people doing the murdering. It could be a single individual on a massive serial spree, or an individual murder per killing which I find just as unlikely. The point is, your stat isn't stating what you think it is
The calculation above is putting an upper limit on the number of murderers (probably, that's discounting groups of participants in murders, but I'm fine with that as serial murderers are far more common than murder groups)
