Always and inevitably everyone underestimates the number of stupid individuals in circulation.
The probability that a certain person be stupid is independent of any other characteristic of that person.
A stupid person is a person who caused losses to another person or to a group of persons while himself deriving no gain and even possibly incurring losses.
Non-stupid people always underestimate the damaging power of stupid individuals. In particular non-stupid people constantly forget that at all times and places and under any circumstances to deal and/or associate with stupid people always turns out to be costly mistake.
A stupid person is the most dangerous type of person.