Always and inevitably each of us underestimates the number of stupid individuals in circulation.
The probability that a given person is stupid is independent of any other characteristic possessed by that person.
A person is stupid if they cause damage to another person or group of people without experiencing personal gain, or even worse causing damage to themselves in the process.
Non-stupid people always underestimate the harmful potential of stupid people; they constantly forget that at any time anywhere, and in any circumstance, dealing with or associating themselves with stupid individuals invariably constitutes a costly error.
A stupid person is the most dangerous type of person there is.