I think both can be true: people who emigrate from a country to pursue better career / life opportunities typically are more industrious in my experience than a

I think both can be true: people who emigrate from a country to pursue better career / life opportunities typically are more industrious in my experience than are those who do not (on average; there are plenty of people who don't emigrate who are just as industrious; it's just that those who are NOT industrious do not emigrate at all), while at the same time some immigrants will differ in industriousness based on their country of origin.