It's quite ironic, but in Chile, mensa is the feminine form
of the slang menso, which means dumb. Example:
Ella es muy mensa
Means "she is very dumb". That's why you probably won't ever find a Chilean in mensa society, or at least not any one that makes it public (which is, of course, the whole point on joining).
A personal thought: it's very easy to be in the top 2% of the population. Just look at the list of the best-selling artists, TV shows, magazines, fast-food chains and politicians that are, obviously, chosen by the other 98%.