From time to time, Mensa will do various promotions to attract new members (like target youth memberships).
Like all Mensa branches, they will only take people whose IQs or standardized test results are in the top 2% but with a population as large as the U.S., that is millions of people!
On a related side note, my brother & I both had our IQs tested as children as part of the G&T program at our school. Growing up, my mom never discussed the actual scores with us, but my brother & I used to speculate over who was "smarter." (Stupid, I realize, but we seemed to argue over everything). Finally, now in my 40s, and in casual conversation about my own two kids, my mom let it slip that my IQ is higher than my brother's IQ. By how much, I do not know...I do not care. But ha, Jim! I TOLD YOU SO!