The smartest aren't uniformly distributed across the Earth.
They almost certainly are, at least before we account for education. Education is, of course, not uniform.
But... the US also has not the best education, so.
That's true. It is possible that the smartest 5% are all here in the USA. But it is statistically unlikely that's true.
They almost certainly are, at least before we account for education. Education is, of course, not uniform.
But... the US also has not the best education, so.