that ("90% of people tend to consider themselves above-average") can mathematically be true if you have a skewed distribution. suppose that 90% of drivers have

that ("90% of people tend to consider themselves above-average") can mathematically be true if you have a skewed distribution. suppose that 90% of drivers have no accidents at all, while the other 10% have 10 accidents per year. Then the average (mean) is 1 accident per year, and fully 90% of drivers are better than average!