This makes sense, if you think about it for more than a moment. If you’re an affluent, skilled worker who can speak multiple languages (include English, the international language of choice), odds are you probably have a pretty good life, and have little reason to seek to immigrate to another country. People who immigrate are typically those who have fewer opportunities in their native lands, and are hungry to come to a new place where opportunities will be more plentiful. If you’re comfortable, you’re unlikely to leave; if you need a better life, you’re more likely to do so.