Blackblade calculates it… from his own perspective.
To each his own… and yet I have to ask if he honestly only places 10 percent weighting on historical and documentary evidence in contemplating other matters. If so, I can’t imagine he spends much time reading books and newspapers. Actually, I have another question. What is meant by the “Belief” factor? I’d also consider substituting “Direct Personal Experience/Observation” for “Lack of any directly observed interaction”.