Per James Wilkinson Sword:
Dunno from other countries, but my feeling is that the average IQ of the USA's population is somewhere South of room temperature.
OK, gross exaggeration... but 100 *is* the "Mean" (whatever that is....).
To be more real, I think my impression is more from people's lack of critical thinking skills - not that mine are all that wonderful... but at least I can recognize my own deficits in that area.