The immigration process itself contains a huge selection bias. Immigrating to America is not an easy process; it's long, confusing and intended to dissuade all

The immigration process itself contains a huge selection bias. Immigrating to America is not an easy process; it's long, confusing and intended to dissuade all but the most persistent of people. Given that, I would expect to find that people who immigrate in general are more intelligent and hard working than an average person.