Varies by country. The US has huge amounts of unselected immigration and makes no real effort to enforce its immigration laws so you get loads of Mexicans and before them Irish and Italians. All of those populations were negatively selected; the average immigrant to the US from those countries was less educated than the average for their country during the period of greatest immigration. Countries with selective or skills based immigration like Australia or Canada, with their points systems have immigrant populations that are a lot more educated than the native population or the average for the source countries.
I remember reading that a large percentage of US companies are founded by immigrants. About 40-50%? Can’t recall sources , but it was a much larger number than what I thought.
