per 20 80 rule, 20% people are just 'not decent' no matter what, it has nothing to do with you, it's just statistics.
now for this small group again, 20% of them are really standing out, I mean really nasty, that makes it 4% of all people, right in the middle of the author claims: 3~5%.
it makes math-sense to me.
on the other hand, I would assume 4% people are genuinely kind and warm-hearted no matter what.
the rest 60%(excluding 20% at both ends), or 92% people(excluding the two 4% at each end) are just regular folks, a mix of selfish and generous day in and day out.