@OmSigDAVID,
You continue to ask questions about the "how" when it's been explained.
Rather than challenging how they arrive at percentages, what is your source of information? Your brain? FYI, that's really, really, unreliable.
Research on such subjects are done from different aspects and people, and the combined consistency provides them with the percentages.
You just can't handle the truth; that's a FACT.