Henrik Rasmussen writes,

estimates of Danes living in London vary between 35,000 and 70,000, which is roughly 1% of the total Danish population of 5.4 million. According to the leading Copenhagen business daily Børsen, the average income of these Danish Londoners is more than $100,000 per year.

Rasmussen uses this statistic, along with others, to debunk the notion that the Danish welfare state is a successful model.

However you feel about immigration (or foreign-born workers), I think that the desires of workers are a useful indicator of relative economic opportunity. I would much rather be in the country with workers teeming to get in than the country with workers teeming to get out.