> Then you don't know enough about how well, for example, African and central Asian refugees or immigrants do in a single generation.

In a generation? I moved here from Europe and within ~6 years accumulated as much wealth as my parents did in a lifetime.

The American dream is still alive and kicking for many if not most immigrants.

But my american friends have a fun joke they like to say: "Wow look at that immigrant work ethic! Wish I could work that hard" ... you could