Carlo M. Cipolla (economist who studied and categorized stupidity)

        1. Always and inevitably, everyone underestimates the number of stupid individuals in circulation.
    2. The probability that a certain person (will) be stupid is independent of any other characteristic of that person.
    3. A stupid person is a person who causes losses to another person or to a group of persons while himself deriving no gain and even possibly incurring losses.
    4. 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 a costly mistake.
    5. A stupid person is the most dangerous type of person.